836 



SUPRA-RENAL CAPSULES. 



the Petromyzon, Ecker only remarks, that the 

 microscopic constituents do not afford any 

 foundation for the view that they are supra- 

 renal capsules. 



III. Development. The supra-renal cap- 

 sules begin at a very early date of foetal life. 

 In the human subject they appear simul- 

 taneously with the kidneys in the seventh 

 week. The mode of their commencement is 

 not yet understood with certainty. Never- 

 theless there is scarcely any doubt that the 

 statement of Arnold, according to which the 

 supra-renal capsules are formed by a projec- 

 tion of the Wolffian bodies, is erroneous. 

 Most embryologists, as Valentin *, Bischoff f, 

 and others, find that another method of begin- 

 ning obtains, namely, that these organs are 

 developed from an independent blastema, 

 which certainly lies very close to the Wolffian 

 bodies, but has nothing at all to do with them. 

 According to Meckel's observations, both 

 supra-renal capsules constitute at first only a 

 single mass ; and Valentin's researches on 

 the embryo of the Dog and Sheep harmonise 

 with this statement. But, nevertheless, this 

 opinion may be founded on an error. Miiller 

 found that the supra-renal capsules of a large 

 human foetus at the eighth week were plainly 

 double, only they lay very closely together at 

 their inferior part. BischofTs extensive re- 

 searches on the embryo of Man and other 

 Mammalia, confirm this statement of Miiller, 

 and explain the error of Valentin and Meckel. 

 The embryonal form of the supra-renal 

 capsules in man is distinguished from the 

 later condition by its being composed of 

 large lobes; and thus, to a great extent, it 

 resembles its permanent condition in some 

 animals. 



It is highly singular that the human supra- 

 renal capsule in the earlier period of foetal 

 life, is not only much larger in proportion to 

 the size of the body than it is at a later 

 stage, but that it also considerably exceeds the 

 kidney in size ($*. 543.). This is shown by 



Fig. 543. 



From an embryo of 8 lines in length. 



a, Supra-renal capsule ; b, Kidney ; c, Sexual 



gland ; d, Wolffian bodies. 



numerous observations of Meckel, Miiller, and 

 others. In a human embryo of the ninth 

 week, Ecker has recently made the same ob- 

 servation. In the embryo of the tenth to the 

 twelfth week, which measures about two 

 inches in length, the kidneys and supra-renal 



* Handbuch der Entwicklungsgeschichte des 

 Menschen, Berlin, 1835. 



v f Entwicklungsgeschichte der SSugethiere und 

 des Menschen, 1842, S. 291. 



capsules are for the first time of pretty equal 

 size. While, on the other hand, in the sixth 

 month the kidneys are, as was found by Meckel, 

 already about double the size of the supra- 

 renal capsules, and their weight is to that of 

 these latter as five to two. And as this com- 

 parative diminution of the supra-renal cap- 

 sules proceeds further, the proportions by 

 weight are in the mature embryo as three to 

 one. And even beyond this time, they expe- 

 rience a continual diminution, so that finally, 

 in the adult, the supra-renal capsule is only 

 l-28th the size of the kidney. 



Strange to say, this extraordinary size of 

 these organs during the foetal period, does not 

 obtain in the other Mammalia. In the earliest 

 period of their embryonal life, the kidneys 

 have always been found considerably larger 

 than the supra-renal capsules. In them both 

 organs appear to grow in precisely equal pro- 

 portion to each other, so that their (compa- 

 rative) weight remains the same in the adult 

 animal as in the foetus. According to Ecker, 

 the supra-renal glands of the new-born kitten 

 are l-56th to 1 -60th the size of the urinary 

 glands. So also the other classes of Vertebrata 

 seem to accord with the Mammalia in this re- 

 spect. At least Ecker observed, in the em- 

 bryo and adult animal of the Coluber natrix, 

 the same relative proportion of size between 

 the kidney and supra-renal capsule. 



If we regard the situation of the supra-renal 

 capsules in the animal kingdom, we shall find 

 a different condition in the different classes. 



It is well known that the Wolffian bodies 

 begin in the embryo at a very early period, 

 and that these, from their structure and func- 

 tion, must be regarded as the kidneys of the 

 embryo ; so that the name of " primordial or 

 original kidneys," may be applied to them with 

 all accuracy. Now these primordial kidneys 

 have a very different duration in the different 

 classes of Vertebrata. In Fishes they remain 

 as the urinary glands during the whole of life ; 

 since in them, as Baer and Rathke found, an 

 organ similar to the kidneys of the higher 

 Vertebrata is never developed. 



The kidneys of Fishes are, therefore, pri- 

 mordial kidneys. 



But in the three higher classes of Vertebrata 

 the fact is found to be otherwise. Here the 

 primordial kidneys pertain to only a part of the 

 foetal life, and then make way for the true 

 kidneys, which are situated beneath the supra- 

 renal capsules. 



Therefore, the supra-renal capsules of fishes 

 are placed on the Wolffian bodies, while in 

 the other Vertebrata they are in connection 

 with the kidneys. 



In Man, in whom the supra-renal capsules 

 are at first uncommonly large, the primordial 

 kidneys disappear remarkably early, so that in 

 the second month they have vanished even to 

 the smallest relics. 



The development of the tissues of these 

 organs is as yet most incompletely known ; at 

 present we have only a single statement of 

 Ecker's respecting it. In a human embryo of 

 twelve weeks, this anatomist found a very 



