Rk. H. Whitehead 351 
embryos, I have ascertained that there are groups of cells which gradu- 
ally disappear and take no part in the production of the adult organ.. 
The cells are in clusters in the central portion of the organ and stain 
very readily, so that they stand out conspicuously in the sections. In 
appearance they resemble the cells assigned to a sympathetic origin in 
the rabbit, and I should feel no doubt that they are.the same were it not 
that I fail to find them in embryos of the second month, so that if they are 
really of sympathetic origin then the union of the two anlages must 
take place at a considerably later stage in man than in other mammals. 
These groups of cells are readily seen in the three-months’ embryo, but 
in the four-months’ embryo they are disappearing and many of the 
clusters are hollow, their eavities being filled with what is apparently a 
coagulum; by the seventh month the clusters have, so far as I have 
hitherto observed, entirely disappeared.” 
J. M. Flint,° in the course 
of a very careful and ex- 
haustive study of the blood 
vessels of the adrenal, de- 
votes a chapter to the histo- 
genesis of the organ, his 
observations being made, Bee 
for the most part, upon pig Cortex, 
embryos. He does not un- 
dertake to determine the 
ultimate source of either 
the cortex or the medulla, ------ Man . 
but he states that the cor- Fra. 1. Diagram of relations of sympathetic ganglia 
Se ea ee nee Bs he F with the adrenal in pig of 35mm. Cap. ad., capsule of 
tex is laid down first, and adrenal; Cap. s. g., capsule of sympathetic ganglia; 
: a F ~. i. S-9-, sympathetic ganglia; Man., mantle layer of cells; 
shows that the medulla is P., prolongations from mantle into cortex. 
developed from cells which 
wander in from outside the cortex. He was able to trace these medul- 
lary cells in the form of small collections passing more and more deeply 
through the cortex as the age of the embryo increased, until finally they 
reached their destination around the central vein. He could follow, 
not only the masses of cells in their migration, but also the arteries of 
the medulla, one arteriole for each collection of cells developing pari 
passu therewith. He expresses decided scepticism as to the derivation 
of these medullary cells from the sympathetic ganglia. 
O. Aichel” introduces a new phylogenetic view. From a study of 
5 Contributions to the Science of Medicine, by the Pupils of W. H. Welch, Baltimore, 
1900, pp. 153-231. 
* Arch. f. mikr. Anat., Bonn, Bd. LVI, 1900, 8. 1-80. 
