490 



GLAND. 



simply formed by the condensation of the con- 

 necting cellular tissue, but in the larger glands 

 a proper fibrous capsule is provided, which 

 adheres more or less intimately to the proper 

 glandular texture. 



General conclusions respecting the minute 

 structure of glands. 



1. That throughout the whole range of the 

 animal kingdom and in every species of gland 

 there is one uniform type, from which the 

 glandular formation in no instance deviates. 



2. That every gland consists of a membrane 

 derived either from the skin or mucous mem- 

 brane. 



3. That this membrane is disposed either in 

 the form of a pouch or of a tube more or less 

 ramified, and terminates in every instance, with- 

 out an exception, in a blind extremity. 



4. That the secreting canals are most diversi- 

 fied in form, being simply sacculated, branch- 

 ing, pennitifid, nail-shaped, or enlarged at the 

 commencement, cellular, berry-shaped, serpen- 

 tine. 



5. That granules or acini in the hypothetical 

 sense of writers do not in reality exist. 



6. That whatever may be the variety of form 

 it is always subordinate to the grand principle 

 which the whole glandular system displays, 

 namely, that the largest possible extent of 

 secreting surface is contained in the smallest 

 possible space. 



7. That there is no immediate connexion or 

 continuity between the secreting canals and the 

 sanguiferous vessels. 



Hypotheses respecting the minute structure 

 of glands. I was desirous in the first part 

 of this article to convey to the reader a com- 

 prehensive view of the glandular structure, 

 unincumbered by any reference to the opinions 

 of anatomists on this subject; but the hy- 

 potheses of Malpighi and Ruysch have so 

 long divided the world of science, that it is 

 necessary to ascertain how far the doctrines 

 advocated by those celebrated men are in 

 accordance with the above-stated conclusions. 

 In doing this, however, much difficulty is 

 experienced, especially in considering the 

 opinions of Malpighi, inasmuch as his com- 

 parisons of the minute structure of the liver, 

 of which organ he principally treated, are very 

 vague and obscure, and being for the most part 

 unaccompanied by illustrative plates, it is 

 almost impossible in many of his descriptions 

 to detect the meaning he wishes to convey. 

 But, notwithstanding these obstacles, it 'is 

 evident, on studying his account of the liver 

 and kidney, that justice has not been done 

 to his researches; for he not only corrected 

 many of the then prevailing errors, but also 

 ascertained several important points connected 

 with this interesting branch of anatomy. 



Malpighi compares the minute lobules of 

 the liver and other conglomerate glands to 

 a bunch of grapes, these lobules being joined 

 to the neighbouring lobules by intermediate 

 vessels. His words are, ' ; for as an entire 

 bunch of grapes is formed of small bunches 

 by a communion and tying together of vessels, 

 which small bunches are themselves formed 



into a mass by appended grapes (acini); so 

 the whole liver is formed by lobules many 

 times folded, and which are themselves formed 

 of glandular globules."* It is thus observed 

 that Malpighi describes in the liver larger and 

 smaller lobules ; and it is to these latter that 

 the celebrated but vague term of acini appears 

 to be more particularly applied. He observes 

 that the lobules are of various forms in different 

 animals ; in fishes having the shape of a 

 trefoil, in the cat six-sided, &c. The inter- 

 lobular spaces are noticed as being distinct 

 in fishes, but as obscure in the more perfect 

 animals. 



With respect to the intimate structure of 

 the small lobules, or acini, Malpighi conceived 

 that each of them consisted of a hollow vesicle, 

 receiving the secreted fluid from the small 

 arteries and conveying it into one of the roots 

 or branches of the hepatic duct ; or, in other 

 words, that the structure of the acinus was 

 the same as that of the simple mucous follicle. 

 Owing, however, to the imperfect means then, 

 possessed of prosecuting such inquiries, it is 

 certain that Malpighi did not detect the ultimate 

 structure; for more exact observations have 

 proved that the last divisions of the secreting 

 canals, although they constantly terminate in 

 ccecal extremities, do not always end in follicles, 

 but that they may consist of serpentine tubes, 

 as in the kidney, or of pennatifid canals, &c. 

 It also has been determined that what he 

 regarded as the last divisions of the ducts, or 

 acini, are themselves composed of smaller 

 canals. But his observations on the develope- 

 ment of the liver in the chick shew that he 

 was acquainted with the essential facts con- 

 nected with the structure of that organ, and 

 with the mode of its formation ; for among 

 other interesting remarks, he says that on the 

 seventh day of incubation the liver of a yellow- 

 ish or ashen colour presents granules of rather 

 an oblong form, and " as it were blind pouches, 

 appended to the hepatic duct."f 



This hypothesis, founded as it is on so 

 large a body of evidence, was generally re- 

 ceived ; but the discovery of the art of minute 

 injection, which seemed to afford ocular de- 

 monstration of the fallacy of Malpighi's theory, 

 induced the majority of anatomists to adopt 

 the ideas rather pompously announced by 

 Ruysch. This celebrated anatomist, rejecting 

 the hypothesis of Malpighi, contended J that 

 he had proved, by injection, that the arteries 

 are directly continuous with the excretory 

 ducts; or that the little ducts proceed from 

 the minute arteries, like lesser from larger 

 branches ; and that each acinus consists prin- 

 cipally of bloodvessels, but contains also an 

 excretory duct. 



In considering the merits of these two hy- 

 potheses, it becomes apparent that Ruysch 

 supported his opinion by evidence of a most 

 insufficient character ; for in investigating the 



* De Viscer. Struct, cap. iii. p. 18. 

 t De Format. Pulli in Ovo, p. 20. 

 t Opuscul. Anat. de Fabric. Gland. Opera 

 otnnia, t. iii. 

 Loc. cit. p. 56, fig. 2. 



