On the structure and use of the spleen

Preface

n^HIS work was written in competition for the munificent prize endowed by the late Sir Astley Cooper, and the Adjudicators — the Physicians and Surgeons of Guy's Hospital — honoured the author by their decision in its favour.

The author, during the progress of his work, received considerable assistance from many to whom he now begs to acknowledge his deep obligations.

In the historical portion of his essay, he received much valuable assistance from his friend, Mr. T. Holmes, in the compilation of the statements and opinions of the ancient writers.

For the large number of analyses of the blood of the spleen, and of the spleen itself, the author is indebted to his kind friend and most able colleague, Dr. H. M. Noad.

The ultimate analyses of the spleen,, as well as some of those on the blood itself, were made by my friend, Mr. Henry Pollock, in the Laboratory of the St. George's Hospital Medical School, under the superintendence of Dr. Noad.

viii

PREFACE.

The dissections recorded in the fourth chapter on the Comparative Anatomy of the Organ, the author owes to the liberality of the Council of the College of Surgeons, who permitted him to have the freest access to their valuable collection of store preparations.

The author, in conclusion, begs to acknowledge his deep obligations to his esteemed friend, Mr, Athol Johnson, who has with much trouble revised the work in its passage through the press.

Part 1. Page

Hippocrates describes its use as serving to draw the

■watery parts of tlie food from the stomach , . 1

Aristotle's opinion similar to that of Hippocrates . 2 Opinions of Erasistratus and Rnfus Ephesius that it has

That it serves to draw the melancholic humour from the

liver (Paulus ^gineta) ...... 3

Galen's opinion of its partial excretory use ... 4 His opinion adopted by numerous anatomists — Valverde,

Columbus, Bauhin, Brunnfelsius .... 5

Estienne's statement of the spleen possessing an excretory duct ........ 5

The overthrow of the Galenic theory by Vesalius . 6 The theory of Ulmus of its elaborating blood from the

chyle 7

The supposition of its being the liver of the left side . 8

Plato's adoption of a similar opinion .... 8

Hoffman's revival of the opinions of Aristotle and Galen. 8

Its reception by numerous writers .... 8

Total overthrow of the Galenic theory by Riolanus . 9

Progress of physiology in the Seventeenth Century , 10

Highmor's elaborate descriiDtion of the spleen . . 10 The opinion of Glisson and Whax-ton that it secretes an

aqueous fluid for the nerves n

X

CONTENTS.

I'AGE

Opinions of Bartholinus 13

Malpighi's elaborate investigations .... 14 Blasius' investigations in its compamtive anatomy . 17 First discovery of its lymphatic vessels . . .17 Mayou's theory of its exciting eifervescence in the blood 18 The theory of Havers that it secretes the synovial fluid 18 The elaborate investigations of Ruysch . . .19 His classification of the ductless glands . . .19 Leeuwenhoek's first accoimt of its mici-oscopical structure 20

Eller's adoption of Malpighi's opinion .... 22

Stukely's theory of its serving as a reservoir for blood . 23 Lieutaud's theory of its mechanical use . . .24 That it serves as an auxiliary in the formation of bile . 25 Winslow's description of its structure . . . .25

Its excision performed in order to ascertain its function 27 De La Sone's memoir on the anatomy of the spleen . 27 Hewson's theory of its converting the lymph into blood globules ........ 29

Assolant's researches on its bloodvessels ... 30 Its excision by Dupuytren ...... 30

Cuvier's theory of its relation with the secretion of the bile and gastric jviice . . . . . .31

Caldani's opinion of its promoting the separation of the

bUe 32

Sir Everard Home's researches . . . . .34 Ojiinion of Treviranus of its converting the lymph into

blood 37

Beclard's analogy of the spleen to the erectile organs . 37 Revival of Hewson's theory by Tiedmann and Gmelin . 38 Hodgkin's opinions of its diverticular use . . .39 Arthaud's supposition of the organ being an electrical ajiparatus

That it serves as a reservoir for blood (Dobson) . . 40 Hake's adoption of a similar opinion . . . .41 The researches of Miiller

CONTENTS.

xi

PAGE

Progi-ess in structuriil anatomy 43

Burdach's theory of its xise 46

Evans's theoiy of its diverticular function ... 47 Oesterlen and Simon's opinion of its storing up nutritive compounds

Kblliker and Ecker's theory of its destroying the blood discs 51

Beclard's analysis of the splenic blood, and adoption of the same opinion 51

Revival of Hewson's theory of its forming the blood discs — Gerlach, Schaffner, Bennett .... 52

PART IL

BEFORE BIRTH.

Reasons for £rst commencing with its development. . 54 Description of the primary intestinal tube and the formation of the liver and pancreas . . . .. ,55

First ajipeai-ance of the spleen . . . . .57

Its origin as a blastemal mass ..... 57

Its distinct separation from the pancreas . . .57 Its distinct separation from the stomach . . . 59 Its close approximation with the pancreas . . .60 Alteration of its position, and approximation to the stomach ......... 60

Concluding observations 62

Development of the Tissues of the Spleen . . 63

Development of the external capsule . . . .63 Development of the trabeculse ■ .... 63 Development of the bloodvessels ..... 64 xii

CONTENTS.

PAGE

Development of tlie blood 66

Development of the pulp of the spleen ... 67 Difference in its structure at certain periods . . 67 Development of the Malpighian vesicles . . .69 General conclusions from the preceding observations on the development of the tissues of the spleen ; .70

Development in the Human Subject .... 72

Its existence. at the 2nd month of fa3tal life. . .72 Distinct from the pancreas and stomach . . .72 The small proportional size of its bloodvessels during foetal life. 73

Development after Birth . 74

When is the spleen largest 1 ..... 75

Table of measurements . . . . . . 76

Conclusions derived from experiments . . . 80

Spleen most active during growth and nutrition of body. 81 Other circumstances modify its size . . . .81

Its variation in size according to the digestive process . 83

Table of experiments ....... 83

Its variation according to the nutrition of the animal . 84

Experiments ........ 84

Other circumstances which modify its size ... 84 General conclusions ....... 85

PART III. Structure of the Spleen 86

Reason for omitting details of exterior anatomy . . 87 Sti-ucture of the peritoneal coat . . . . .87

Structure of the fibrous coat 88

Structiire of the trabecular tissue . . . .90

CONTENTS.

xiii

PAGE

Structure of the larger trabeculse .... 92 Structure of the microscopic trabeculse . • • 96 Muscular fibre cells in tbe capsule and trabeculse of the

1 . . 99

spleen

Conclusions from the preceding investigations . . 101 On the. contractility of the spleen . . • .102

Experiments detailed 103

Conclusions derived from experiments . . .105

The splenic artery . . . • • • .106 Its peculiarities at various periods of life . . .107 Its si2;e, thickness of its coat, &c. . . . .108

Sheaths of the arteries in man . . . . .109 Sheaths of the veins in man . . . . .110 Sheaths of the vessels in animals . . . .111

Minute structure of the sheaths 112

Distribution of the splenic arteiy . . . .114

The isolated distribution of its branches . . .115 Capillary plexus of the spleen . . . . .117

Termination of the capillaries . . . . .118

Distribution of the arteries in the mammalia . .119 The splenic vein ........ 120

Its origin, course, termination, size, &c. . . .121

Distribution of its branches in the interior of the spleen. 122 The isolated distribution of these branches . . .123 Varied mode of origin of the smaller veins. . . .124

Size of the smaller veins . . . . . .129

Structure of these veins . . . . . .130

Their relation with the other elements of the spleen . 131 Distribution and stracture of the veins in the mammalia. 132

On the Blood of the Spleen 136

Great importance of this part of the investigation . 136 Microscopic and chemical examination of the blood , 137

■^^v CONTENTS.

PAGE

Method of conducting the investigation . . .137 Variation in the quantity of the blood . . .139 Modified by the digestive process . . . .140

By the nutrition of the animal, &e 140

Its rate of coagulation, specific gravity, &c. . . .144 Microscopic examination of the blood . . . .145 The difference it presents as compared with other blood 145

Cliemical Analysis of the Blood of the Spleen . 152

Results obtained from these analyses . . . .152

Important differences between it and other blood detected ......... 152

Table showing the amount of water and solid matters . 154 Conclusions derived from these analyses . . .155 Differences in the amoimt of seinun and crassamentum . 155 Diminution in the amoiint of the blood globides . .156 Varied by certain conditions . . . . .158

Increase in the amount of fibrine . . . .160

The causes which appear to vary its amount . .161 Increase in the amount of albumen . . . .162

The causes which vary the amount of this ingredient of the blood . . . . . . . .163

Reddish colour of the serum of the blood . . .164 Analysis of the serum of the blood . . . . 1 65

Results of these analyses 166

Analyses of the salts of the blood . . . .169 Conclusions derived from these analyses . . .170 Amount of iron in the blood . . . -. .171 General conclusions from the preceding investigations on the blood of the spleen . . . . .172

The elements of which it is composed . . . .178

Parenchyma cells of the spleen 178

Their stiaicture . . • • • • ■ -179

CONTENTS.

XV

PAGE

Their variation in quantity 182

The laAvs which regulate these quantitative differences . 182 Their chemical composition . . . . .183 The colom-ed elements of the pulp . . • .186

Of what they consist 186

Theii- structure in man and animals . . . .187 The situation of these elements . . . . .192 In what manner the changes described in them occur . 195 What laws regulate their occurrence . 196

Their chemical composition . . . . .198

Chemical Analysis of the Spleen 202

Proximate analysis ....... 203

Absence of kreatine ....... 204

Absence of lU'ic acid and hypoxanthin . . .208

Distillation of the fatty and other acids of the pulp . 210 Determination of lactic acid . . . . .214

Analysis of the inorganic compounds of the pulp . 216

Ultimate analysis of the pulp . . . . .219

General conclusions . . . . . . .219

Their fonn, size, number, consistence, colour, &c. . . 222

Their situation and connexions ..... 224

Structure of their capsule . . . . . .226

Their relation with the arteries and capillary plexus . 231

Their relation with the veins . . . . .233 Are they connected with the lymphatics 1 . . . 235

Contents of the corpuscles 235

Their chemical composition . . . . .239

Their variation in size ...... 240

Causes modifying this difference in size . . .241

Modified by the digestive process and nutrition of the animal ......... 241

Modified by the kind of food and the introduction of fluids 245 Their nature determined . . . . . .247 xvi

CONTENTS.

PAGE

The Lymphatics of the Spleen 249

Origin of the superficial lymphatics La the horse . . 249

Origin of the deep lymphatics 250

Their course and termination ..... 252 The lymphatics in the human subject .... 253

Of the lymph 254

Colour and microscopic characters of the lymph from the

superficial lymphatics ...... 254

Colour and microscopic characters of the lymph from the

deep lymphatics ....... 255

Quantity of the lymph 258

Composition of the lymph . . . , . .259 Results derived from the above iavestigations . .260 Fimction of the splenic lymphatics . . . .262

Nerves of the Spleen 263

Origin of the splenic plexus . . . . .263

Course of the plexus . . . . . . .265

Distribution of the plexus in the interior of the spleen 266 Minute struct\u-e of the nerves . . . . .268

Their mode of termination . . . . .270

Nerves of the spleen iu animals . . . .271

Part IV

Table showing the proportion the spleen bears to the body in the difierent vertebrate classes . . .273

Mammalia ^'^^

CONTENTS.

xvii

PAGE

Insectivora. Tupaia Javanica, sorex . . . .276

Amphibia. Phoca vitiilina — the large size of the organ in this class, used as a reservoir for blood . . . 279

Marsu2naUa. Variation in the size of the spleen according to the habits of animals, as seen ia this order. 281 Its dissection in the dasyurus ursinus, phalangista fuliginosa, perameles nasutus, macropus major, petaurus sciurus ........ 281

Rodentia. The spleen has no relation with hybernation. Its small size in this class. Its dissection in mus Alpinus, mns coypus, hydromys, dipns, mus rattus, sciurus vulgaris, sciurus quadrivittatus, sciurus niger, hystrix cristata . . . , . . .282

Edentata. Extreme difference in the size of the spleen in this class varied by the habits of animals. Its dissection in the bradypus tridactylus, orycteropus, myrmecophaga jubata, dasypus. . . . . . 284

Monotremata. Its smaU size in the echidna. Large in the omithorynchus — this peculiarity explained . .286

Cetacea. Its dissection in the porpoise and in the balsena mysticetus. Its small size in this class as compared •with the amphibia. This peculiarity explained. . 290

General conclusions from the above dissections . . 292

Minute structure in mammalia 293

Dissection of the spleen in the cormorant, puffin, oyster bird, spoonbill, Virginian owl, ostrich, moor-hen . 295 xviii

CONTENTS.

PAOE

Minute structure of the spleeu . . . .297

. 297 . 298 . 301 . 303

Structure of the fibrous coat and trabeculae The Malpighian bodies The pulp of the spleen in birds .

Bloodvessels and blood of the spleen

Reptilia 304

Diminished size of the spleen in the lower vertebrata . 304 Glielonia. Testudo Eiu-opsea, testudo mydas . . . 304 Emydoscmria. Orocodilus, alligator . . . .306

Sawia. Lacertidse, lacerta gecko, lacerta calotes, lacerta chameleo ......... 306

Ophidia. Existence of the spleen in this class, though of small size. Its dissection in the boa, hydrus, coluber natrix, viper, natrix torquata, typhlops, amphisboena, anguis fragilis ........ 307

Minute structure of the spleen in reptilia . . .312 Structure of the external tunic different in the ophidia to what is seen in the other genera . . . .314

Ai'rangement of the bloodvessels . . . . .315

The differences they present in various genera . .315 Structure of the pulp . . . . . . .316

The splenic blood • • 320

General conclusions from the above investigations . 320

Pisces 321

The proportional weight, position, bloodvessels, &c., of

^22

the spleen in fishes

CONTENTS.

xix

PAGE

Dissection of lepidosiren . . . . . .323

Dissection of lamprey ....... 324

Minute structiu'C of the spleen in fishes . . . 325 Fibrous capsule and trabecute ..... 325

Structure of the pulp . . . . . . .326

General results furnished by compai^ative anatomy . 338

PART V. Physiological Conclusions 340

ON

THE STRUCTURE AND USE

OF

THE SPLEEN/

Part I. Historical Introduction

IN the imperfect records left of the anatomy of the ancient Egyptians, no trace of any knowledge of the spleen can be ascertained.

In the Treatise ' De Carnibus,' ascribed to Hippocrates, the following peculiar account of the organ is given : — ' The spleen is composed thus : with the hot and the viscid (principles) a great deal of the hot and very little of the cold, only so much as is sufficient tofix the viscid part of it ; that is, the fibres which are in the spleen : and it is through these fibres that the spleen is soft and fibrous.' ^ He states that its use was to draw the watery part of the food from the stomach, as the gall-bladder draws the bile from the liver. Its shape resembles the print of the foot, and

^' The etymology of the word is doubtful ; the ancients state that the word o-ttXjji' is derived from (T7r\ayx>'ov (a viscus), othei-s derive it from the Greek word o-Traw (traho), to cbuw, because they supposed that it drew to itself the spoiled parts of the blood.

2 Hippocrates. De Carnibus. b.c. 431.

B

HISTORICAL INTRODUCTION.

that next to the head is the most hollow part, and is full of cavities and has most spaces, having also wide and thick veins of a spiral form. (Hippocrates De Anat. et de Morhis.) He notices also the diseases of the organ and their treatment in his works De Internis Affectionibus, and De aere, aquis, et locis.

The celebrated Greek philosopher Aristotle, at a somewhat later period,' described its position and attachments in the human subject ; he noticed also its connexion with the great vein, (vena porta3.) In his dissections of animals he observed that those which are oviparous have the organ so small as to have escaped the notice of some, as in most birds and some of the reptilia — a fact confirmed by many since his time. He believed that its use was to draw away the superabundant moisture from the stomach, and to assist that organ in digestion.

Diodes of Caristus, who flourished a little time after Aristotle, confirmed the statements which his predecessor had advanced.

A period of repose ensued for several centuries, until two celebrated anatomists arose in the Alexandrian school, who, favoured by the permission of Ptolemy Lagus, the first of the Egyptian princes, with diligent research elaborately dissected the human body. These were the celebrated Herophilus, and Erasistratus, the pupil of Chrysippus, his contemporary ; their researches were such as completely to overthrow the mystic opinions of many of their

' AiiiSTOTELES, De AnimaUmn Historid. Lib. x. pp. 23, 44, 46, 57.

HISTORICAL INTRODUCTION.

predecessors, and were the means of giving to anatomy the rank of a true science. They did not, however, advance much the anatomy of the spleen, for the latter author states that it has no function ; but his followers, condemning the negligence of their teacher (as Galen states), said that nature gave animals a spleen to prepare the chyle expressed from the food, for the liver, for the generation of blood.

Celsus merely refers to its position, and its soft and thin nature, not giving any account of its structure or probable function.'

Rufiis Ephesius^ does little more than allude to its position. Its colour he likens to wine lees ; its consistence loose and spongy, and composed of a network of vessels, inactive, and without vital energy ; he states that it has no use.

In the works of Aretseus* and Paulus -lEgineta'' no fresh addition appears to have been made to our knowledge of the anatomy of the spleen, the latter author believes that its use is to attract from the liver the melancholic humour which is, as it were, the lees of the blood, the superfluous quantity being expelled

3 Aret^i, Oappadocis, Opera Omnia. Lipsise, 1828.

* Paulus ^gineta. Translated from the Greek by Francis Adams. Sydenham Society, Vol. i. p. .'577.

B 2

HISTORICAL INTRODUCTION.

to the orifice of the stomach to excite the appetite. This physiological conclusion he then applies in explanation of the pathological changes produced in the system by disease of the gland.

Julius Pollux,' at a somewhat later period, merely notices the existence of the gland, and mentions that its position is on the left side.

The views of the function of the spleen about this time advanced by one of the most celebrated of all the ancient physiologists, Galen,' are interesting, as they are founded upon the results of anatomical examination, and the almost universal assent with which these opinions were received for many years, showed the respect with which all the statements of this great philosopher were entertained. He believed that the spleen attracted, by its great vein, the thick and muddy juices generated in the liver, and, after undergoing some changes in the substance of the gland, materially assisted and perfected by the arteries, part of this juice was transformed into aliment for the spleen, whilst that part not capable of transformation was transmitted by a series of veins into the cavity of the stomach in the form of an excretion.

This opinion as to its function received universal assent, not only from the physiologists of his time, and the Arabians, Avicenna, &c., but prevailed through the

1 Jul. Pollucis, OvonatrriKov. "Vol. i. p. 259.

2 GcAiiEm Opera, De usu partium corporis. Yenetiis, 1550. Vol. i. p. 140, cap. 15, 16; lib. iv.

ages of darkness and barbarism, and was even defended by those anatomists who lived in the commencement of the 16th century, at a time when science and lite-" rature were again revived, and when the intellectual powers became again roused, after a repose of more than a thousand years. Thus Guinterius' follows Galen's description of its structure almost in the same words, and believes its function similar to that ascribed to it by that celebrated writer.

Estienne^ not only adopts the same opinion of the spleen excreting the melancholic juice, but states that there is a common duct from that organ to the stomach, by which the black bile regurgitates to its orifice, the use of this fluid being, as he remarks, to incite the appetite, and by its bitterness and acidity desire is produced. He also supposes that, in conjunction with the liver, it warms the stomach, and aids in the digestion of the food. There can be hardly any doubt, from the account given by this author, that he supposed the vasa brevia distended with blood to be ducts proceeding from the spleen to the stomach — an opinion soon afterwards set aside by the accurate observation of Yesalius. Although the outward form, position and attachments of the organ, as well as the course of its vessels, are mentioned

Chaules Estiennis, La dissection das imrties du corps hvmcdn. Paris, 1546. Pp. 189, 197, 383.

HISTORICAL INTRODUCTION.

^vith tolerable accuracy by Valverde,' Colombo;^ Brunnfelsius,^ and Bauhin/ in the same century, their description of the minute structure of the gland is imperfect, and their opinions of its use either precisely similar, or only a slight modification of Galen's.

In the same century, however, there lived some anatomists who did not bow down to the authority that Galen's learning and philosophy had inspired in nearly all, and there are none, perhaps, who assisted more to overthrow the doctrines advocated by him than Vesalius,^ one of the greatest anatomists of that age. This author, although he did not suggest any new theory of its use, except his supposition that it assisted digestion by means of its own innate heat, concluded, from his more careful and accurate examination of the vessels of the gland, that no channel exists like the bile duct, to convey the recrementitious matter into the stomach, and that

^ Brunnfelsius, O. T., Catofo(/its. Ju.Medicor. 1530. P. 14. BauhinIj Caspari, Anatomica cor2)oris vinlis et mvZiebns historia. Lugdimi, 1597. Pp. 56 — 58.

^ A. Vesalius, Oj)era Omnia Anaiomica. Lugdmi. Batav., 1725. Pp. 437 to 440.

HISTORICAL INTRODUCTION.

the veins going there, do not arise from the substance of the spleen, but from the veins just before they enter into it; he observed, also, that their contents did not differ from that of other veins. It was by means of these simple anatomical observations that he overthrew an. opinion advocated by one of the most celebrated physiologists, an opinion which, as we have seen, was supported by many able anatomists and taught in the ancient schools for more than a thousand years.

About this period a new theory of its use was suggested by Franciscus Ulmus,^ in his Monograph, the first then published on the anatomy of this gland ; a theory, however, not founded on extended observations on the anatomy of the organ. He supposed that its office was to prepare blood for the heart and arteries ; the material from which it is formed being the chyle, which is brought from the stomach by a large vein (the gastric) to the spleen, and by a branch of the vena portse, the formed blood being returned to the heart by the splenic artery and aorta. Pel. Plater^ also believed that its office was rather in the elaboration of blood, than in the attraction of the melancholic juice, although he explained the method by which it was elaborated differently to Ulmus. This author also argued that as all azygous parts are placed in the median line of the body, the spleen cannot be one, as it

Fel. Plater, De corporis hvmcmi structwd et usu. Basil, 1583 P. 185.

HISTOEICAL INTRODUCTION.

corresponds in situation and structure with the liver, and therefore must be the liver of its own side, an opinion which he attempted to prove by many arguments. Plato, in Tima3us, makes mention of the same fact.

Hoffman,' in his Essay, considers chiefly the opinions of the ancients, and more particularly those of Aristotle and Galen, regarding the structure and use of this gland, adding no original observations. He then defends Aristotle's opinion, and makes his o"\vn suit both Galen's and Aristotle's. His own appears to be that it draws to itself the thinner and more watery parts of the blood, and of the chyle, just as it is undergoing transformation into blood, and separates from it (the chyle) the earthy particles forming the black bile, as an excrement, and also secretes blood of a thinner character than that of the liver. Veslingius" and Marchettis' also about the same period adopt a similar view. Spigal* adheres to the opinion of Aristotle, that it, with the liver, assists the digestion of the food ; he also adopts the views of Hoffman, and oddly observes that, as it purges the blood of its thick

1 Casp. Hoffmannus, Be um lienis, cerebri, et de icJioribus. a.d. 1639. Lugd. Bat.

A. Spigal. Amsterdami, a.d. 1645.

HISTORICAL INTRODUCTION.

humours, it is theTefore larger in man than in other animals, as he, being the wisest of animals, requires the purest blood. ' Ut defecari sanguis felicius queat acrassis humoribus, cum homo animal sit sapientiae studio addictum, at sanguis quo tenuior est et purior, eo sapientiores reddere dicitur.'— Arist. lib. ii. de part. Animant. cap. 11, p. 242.

In the description given by Riolanus\ he brings forward many observations, original in themselves, which show the incorrectness of Galen's opinion, viz., that the spleen is nourished by the melancholic juice; he shows, for instance, that the blood found in the spleen is no different to that found in the liver; that the splenic vein does not arise from the liver; and that no evacuations of black humour are ever found in the stomach or intestines of healthy subjects; a fact that might easily be observed, if such were conveyed by the spleen to that organ. Yet notwithstanding these observations, so^ impressed was he -svith the authority which the ancients inspired in nearly all, that he brings forward an opinion on the use of the gland that reconciles those of Hippocrates and Aristotle with that of Galen, The anatomical knowledge that was hitherto possessed appears merely to relate to the outward form and connexion of the several organs — a task which the first great Italian anatomists achieved; but no very considerable progress had as yet been made in the minute structure of the several organs, to determine which was the only

^ Johannes Riolanus, 0^;em Anat. Paris, 1649. Pp. 129 to UO.

HISTORICAL INTRODUCTION.

sure road for the advancement of any knowledge regarding their use. The celebrated discovery, however, of the circulation by Harvey' about this period, and Aselli's^ careful observations on the course of the lacteal vessels, served not only to dispel many of the preceding erroneous doctrines, but also assisted, more than perhaps any other discoveries, in the furtherance and enlightening of physiology.

Although some traces of these more minute investigations may be found in some of the preceding writers,^ little progress was made in this department of anatomy until about the middle of the seventeenth century. About this period, Highmor^ gives a far more minute description of the spleen than any j)receding writer. He describes its external tunic, and the trabeculas, as arising from its inner surface ; these latter being solid fibres which form complicated nets around which the parench5ana adheres. The vessels he also describes very minutely, both in man and animals, and points out the differences between them, mentioning the existence of valves in the veins of the latter, which prevent the reflux of blood into the spleen. Notwithstanding these more extended observations on the structure of the gland, his opinion

1 Harveii Exercit. Anatomica de motu cordis, et sanguinis drculatione in animalihus. Francof. 1628.

3 Vesalius, Riolanus, Baudin.

HISTORICAL INTRODUCTION.

of its function is singularly unhappy, as by his own statement it refutes itself. He believed that the melancholic juice was brought to the spleen by the arteries from the coeliac, after it has undergone its last concoction in the heart; that the spleen ferments and separates it, applying a portion of the separated blood to its own nutrition ; what is left of the purer blood flows by the splenic vein through the liver into the cava, and then to the heart, that it may acquire heat and spirits from the heart, and be driven free from aU excrement by the aorta for the nutrition of an parts.