Xo. 490] NOTES AND LITERATURE 



667 



first appear in the yolk sac, but later they are formed from the endothe- 

 lium of blood vessels w ithin the embryo. A section of the aorta of a 

 rabbit of 10 days and 5 hours showed a rounded mass of lymphocytes 

 projecting into its lumen and still connected with its endothelium. 

 The lymphocytes give rise to other lymphocytes and to the jx;rmanent 

 erythrocytes. The latter are smaller than the primary erythrocytes; 

 they are formed from lymphocytes throughout life, and ultimately, 

 l)y the cxtrnsion of their nuclei, they become the red corpuscles. In 

 ihc v( ss(>ls of tlic yolk s:ic at 12 days there are three kinds of corpuscles, 

 n.iincly priniiiiy cvytlinx ytes, lymphocytes, and permanent erythro- 

 < yi(vs. In il)c HU'sciichyiua iiround the medullary tube of the embryo 

 of 12 days, two small waiKh^ing cells were shown. Tliese cells arise 

 in the mesenchyma; in the bone marrow they come from cells like 

 lymphocytes in the periosteal mesenchyma. The giant cells of the 

 marrow were classed with the lymphocyte series. 



In addition to these preparations Professor ^^a.\l^u»^\ ^llo^^c(l two 

 others of much interest. One of these A\;i.s a >r< iioii of ilic tliMiiu,^ 

 of a rabbit embryo of 15 dr.ys. The solid r|uilH-lial n.as>rs ^^rvr 

 being invaded l)y lyni])h()cytes ; the e{)itho]ial cells were not beconiing 



other ])re|.!iration \\a^ from a rabbit's kidney which had become 

 atrophic, followiiio- i1h- lipition of the renal vessels. In the kidney 

 calcification and bone fo'nnation ha<l occurred, and a well defined 



but never in other animals siniilavlv i n-ate.l. 



Mme. W. Dantel.akofV of St. i'eier^l.nr- .lenion-trate.l the forma- 

 tion of the blood corpuscles in tli.' e|n< k. A se- tion from an embryo 

 incubated 68 hours, showed cells ' ' ' ^ ^ 



