980 



Now about the giant-cells in tlie cat's liver. These are quite 

 similar to those of tiie spleen but at birth they are less abundant. 

 After birth they disappear gradually, so that only few remain in 

 tlie 4"i week. However, never did I find an instance of degeneration 

 as is encountered in the spleen. 



r-. ^^ 



Fig. 5. Embryo guineabig 9 cm. long. Spleen nearly 1000 X 



natural size. a. megakaryocyte lying in the lumen of the vessel, with 



a process still in the wall. h. lumen of the vessel, c. vessel wall. 



Because I would, not limit my research to one species of animal, 

 I also studied the guinea-pig in quite the same way as I did the cat. 

 The result was nearly the same. In the guinea-pig the critical moment 

 does not occur after, but before birth. This, no doubt, is explained 

 by the fact that the cavia has already before its birth reached a 

 stage of development that is attained by the cat only much later. 

 The extrusion-process showed itself most distinctly in the veins 

 of an embryo 9 cm long (from head to caudal bend) (Fig. 5,a) I 

 would have studied earlier stages of suitable caviae, had any been 

 at my disposal. The maximal number of giant-cells of the spleen is 

 smaller in the guinea-pig than in the cat. In guinea-pigs 1 did not detect 

 such a typical degeneration accompanying the extrusion as in cats. 

 My failure in finding the most appropriate stage is perhaps respons- 

 ible for this. In a cavia of 17 days the number of giant-cells has 

 already diminished to a number not larger than is assigned by 

 De Kervily for the adult cavia, viz. 3 per 25 mm\ 



SUMMARY. 



1. In the cat's spleen a process is most distinctly demonstrable 

 in the second week after birth, in v/hich the megakaryocytes pro- 

 trude into the large veins and break up into pieces through degeneration. 



2. This process is not a formation of thrombocytes. 



3. A similar process takes place in guinea-pigs shortly before birth. 

 1 would take this opportunity of thanking Dr. A. B. Droogleever 



