. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 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-re
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 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 #, Bischofff, 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 MeckeFs 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. Bischoff's 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 (fig.
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