839 



SUPRA-RENAL CAPSULES. 



a network of capillaries, while it includes 

 within its interior, glandular contents in very 

 diverse forms. These contents consist, in 

 general, of elementary granules, of an albu- 

 minous material, of fatty granules and small 

 drops of fat, and of nuclei and cells in the 

 most variable quantities. Cells, which are 

 the highest development of glandular contents, 

 are not always found : more frequently only 

 nuclei are noticed. It will be recollected that 

 in speaking of the contents of the supra-renal 

 capsules, we have stated that the development 

 of cells occurs by the method of circumposition 

 of a globular membrane, and the same method 

 obtains in a number of the glands. 



The first two of the three forms of glands 

 frequently occur isolated, and thus exhibit 

 microscopic glandules of the greatest sim- 

 plicity ; as for instance the stomach glands of 

 Mammalia, the glands of Lieberkuhn, the cu- 

 taneous glands of the Frog. In other instances, 

 glandular tubes or sacs are connected to each 

 other in very variable number, and thus form 

 the larger glands. In this way the kidneys 

 and testicles originate from tubes ; while from 

 sacculi are formed the multitude of clustered 

 glands, as those of Brunner, the salivary 

 glands, and the pancreas. 



The first two forms of glandular structure 

 have no further interest as regards our present 

 object ; but the case is very different with re- 

 spect to the third or vesicular form. 



The gland-vesicles have a very diverse size, 

 ranging from microscopic dimensions to a 

 quarter, a half, or even a whole line or more. 

 Their shape is always spherical, so that their 

 membrana propria encloses a globular cavity, 

 which contains, suspended in a fluid, all the 

 different constituents of gland-contents pre- 

 viously spoken of. In very numerous experi- 

 ments I have never found vesicles of this kind 

 further divided by ensheathing membranes. 



Generally the united gland-vesicles are in- 

 laid in the fibrous tissue of the particular 

 mucous membrane of the body ; they are 

 sometimes in greater, sometimes in smaller 

 quantity, so that great differences, both in- 

 dividual and generic, may be noticed in this 

 respect. In many places they occur with 

 greater frequency, so as to constitute the rule, 

 and have therefore received a special name. 

 For instance, the glandulae solitariae of the 

 intestine, and the lenticular glands of the 

 mucous membrane of the stomach, belong to 

 this category ; while in other cases more 

 than one or even many vesicles of this kind 

 are grouped together to form a glandular body 

 of some extent. Amongst such aggregations 

 may here be enumerated the Peyerian vesicles, 

 which form a single layer of this kind in the 

 mucous membrane of the intestine. We find 

 the same grouping in the ovary, where these 

 vesicles are called " Graafian," in honour of 

 their discoverer. But here they are some- 

 what more widely separated from each other 

 by the thickness of a solid fibrous basis, or by 

 the so-called stroma ; and they enclose, beside 

 the usual glandular contents, a peculiar body, 

 the primitive egg or ovum. 



The physiological relations of the gland- 

 vesicles, and especially their duration and 

 origin, are as yet little knov/n. The facts 

 may probably be stated as follows. The 

 gland-vesicles arise from cells which enlarge, 

 so that the cell-membrane becomes the wall 

 of the vesicle, and its contents form those 

 of the vesicle also. At least I have ob- 

 served exactly this occurrence to take place 

 in formation of vesicles in a fish of very 

 low development which inhabits our brook 

 (Ammoccetes branchialis). In this fish a num- 

 ber of glands of this kind may be found at 

 the dilated part of the intestinal canal, on both 

 sides of it near the spiral fold : these remain 

 tolerably small, although they experience con- 

 siderable variations of diameter. They are 

 densely filled with large, pale, smooth nuclei, 

 of oval or roundish form, the number of which 

 is greater or smaller according to the size of 

 the vesicle. Beside these are seen in the tissue 

 of the wall of the intestine separate cells, 

 which enclose two nuclei in no way distin- 

 guishable from those of the gland-vesicles. 

 From these cells they pass, by all intermediate 

 gradations, to the large vesicles. If one may 

 generalise on this observation, it may be stated 

 therefrom, in accordance with the proposition 

 mentioned above, that the shut gland-vesicles 

 proceed from cells. The gland-vesicles in the 

 mucous membranes of the Mammalia are very 

 unfavourable objects for examination ; so that, 

 unfortunately, in spite of many attempts, I 

 have not been so lucky as to observe their de- 

 velopment. So also I am unable to state in 

 what way the multiplication of nuclei takes 

 place, whether by a fission of the nuclei already 

 present, or whether new nuclei arise inde- 

 pendently of the old ones in the fluid of the 

 gland. But I conjecture that the latter is 

 the case. 



By their further increase of size, the gland- 

 vesicles come to lie more on the surface of 

 the substance in which they are imbedded. 

 But the membrana propria does not possess 

 an unlimited extensibility, so that a period 

 arrives when it can no longer withstand the 

 contents, and 'is burst by them. This rending 

 occurs at the place of least resistance, namely, 

 at the upper and most external part, and en- 

 gages not only the membrana propria of the 

 gland-vesicle, but also the thin layer of fibrous 

 tissue present superficially to this. By the 

 occurrence of this so-called dehiscence of 

 the gland-vesicles, its fluid contents become 

 effused amongst the other constituents. This 

 process has long been known to occur in the 

 Graafian follicle of the ovary ; but it may 

 also be seen with the greatest distinctness in 

 the vesicles of the mucous membranes, as well 

 in the separate as in the Peyerian glands. 

 The burst gland-vesicle is thus brought into 

 connection with the outer world, und now 

 resembles a wide-bellied and short-necked 

 flask : it has thus suddenly become converted 

 into a small sac, such as we have already 

 found as a constituent of the glands treated 

 of as belonging to the second variety. 



After their dehiscence, the gland-vesicles 



