130 VICTOR E. EMMEL 



posed while still beating, grasped by its tip with a small forceps, 

 severed from its vascular connections, and quickly brought into 

 contact with the surface of a clean slide, the drop of blood thus 

 deposited on the slide being disturbed as little as possible. A 

 few of these preparations were allowed to dry in the air as in 

 Engel's method, but as this procedure is open to criticism (Weiden- 

 reich '04, p. 373, and '11, p. 371) the greater part of the slides 

 were inverted in a closed chamber and the blood cells fixed by 

 exposure to the vapor of either 10 per cent formalin or 1 per cent 

 osmic acid according to Weidenreich ('11), stained with Giemsa 

 in the proportion of 2 drops of Giemsa to 1 cc. of distilled water, 

 Maximow ('09, p. 457), with Erlich's triple stain, or Wright's stain. 

 In addition to the fixed preparations, hanging drops of the fresh 

 blood were studied microscopically in a warm chamber maintained 

 at 38° to 40° temperature. 



Confining our attention to the large nucleated erythroblasts, 

 it may at once be stated that with regard to form the results of 

 the first observations of these preparations seemed to substan- 

 tiate Engel's account, for in the fixed as well as the fresh blood 

 the appearance of the erythroblasts is such that, if no other 

 methods be employed, one is readily lead to the conclusion 

 that they are typically characterized by a rounded or spherical 

 contour. However, a subsequent study of blood cells fixed in 

 situ in the embryonic vessels of the foetal membranes yielded 

 different results. These membranes, chorionic, allantoic, and 

 amniotic, were fixed by immersion in Zenker formalin, that is, the 

 usual Zenker mixture in which the 5 cc. of glacial acetic is replaced 

 with 10 cc. of strong formalin, as recommended by Maximow ('09). 

 These membranes were stained with Giemsa and mounted in toto. 

 Upon examining the blood corpuscles thus fixed in the vessels it 

 soon became evident that the erythroblasts were by no means all 

 spherical in form. On the contrary, many of these nucleated cells 

 were distinctly flattened biconcave discs, others bell shaped (figs. 

 3 and 4, e) . These forms were so abundant it became evident either 

 that previous conclusions were erroneous, or that the forms other 

 than spherical were the results of faulty technique, although the 

 latter seemed* questionable since in all other respects the nuclei 



