and Laboratory Methods. 



1365 



At first sight the spermatozoon of 

 the rat (Fig. 9) reminds one of the 

 immature male cell of the bird, and 

 it is not impossible that these cells 

 may undergo further development. 

 The spermatic fluids of both white 

 and gray rats were studied, and 

 no marked difference was found to 

 exist between these cells. The 

 head and tail of this cell stains 

 well, the concave border of the 

 head staining slightly deeper than 

 its body. Measurements were 

 found to be : 



Fig. 9.— White Rats. 



Total length, 

 Length, head, 

 Length, tail. 



0.225 to U.288 mm., or 0.0087 to 0.0092 in. 

 0.012 to 0.016 mm., or 0.0004 to 0.0006 in. 

 0.209 to 0.222 mm., or 0.0081 to 0.0086 in. 



The spermatozoon of the guinea 

 pig (Fig. 10) differs widely from 

 any other member of the series. 

 Its head is nearly spherical, and a 

 minute, deeply stained portion was 

 noted at the junction of the tail. 

 Each head was provided with a 

 neatly fitting, semi-lunar cap, which 

 was also well stained. At times 

 these caps were seen detached, and 

 at others deformed, giving that 

 portion of the head either a con- 

 cave or a pointed appearance. 

 That portion of the tail nearest 

 the head was always deeply stained, 

 and the course of the tail was 

 never found to be tortuous. The 



Fig. 10.— Guinea Pig. 



following measurements were obtained for these cells : 



Total length, . . 0.113 to 0.138 mm., or 0.0053 to 0.0057 in. 

 Length, head, . . . 0.006 to 0.012 mm,, or 0.0006 to 0.0004 in. 

 Width, head, . . 0.007 to 0.011 mm., or 0.0004 to 0.0004 in. 

 Length, tail, . . . 0.125 to 0.132 mm., or 0.0048 to 0.0051 in. 



L. Napoleon Boston, M. D. 

 Philadelphia Hospital. 



