BLOOD CORPUSCLES 129 



part of their extent are composed of the marginal layer 

 of alveoli only, which comes into close contact with the 

 central nucleus. The blood corpuscles possess, in addition, 

 an internal cavity filled with cell sap, in which I occasionally 

 observed indications of isolated radial tracts of protoplasm ; 

 I have not, however, followed up this point more closely. 

 Studying the surface of the corpuscle by accurately 

 focussing its superficial aspect, it may be observed that the 

 network of the alveolar layer is more or less fibrous in 

 nature, as is represented for a small portion of Fig. I, a, at o. 

 The cell nucleus (n) shows a very distinct, rather delicate 

 framework of meshes, which stains a beautiful blue with the 

 method of preparation mentioned. In the nodal 'points of 

 this nuclear framework numerous chromatin granules of a 

 red colour are lodged, as I have briefly described already 

 on a former occasion (1890). As the figure shows, the 

 meshwork of the nucleus is much more open than that of 

 the entirely unstained protoplasm, and is distinguished from 

 the latter, therefore, not only in colour, but also in struc- 

 ture. Since this is also so distinct and clear in many other 

 cases, it seems difficult to understand how it is that the 

 theory of a direct transition between the framework of the 

 protoplasm and that of the nucleus is continually finding 

 new adherents. 



Although it is impossible for me to enter here into the exten- 

 sive literature upon the subject of blood corpuscles, I must con- 

 sider some more recent observations, without setting up any 

 pretence to completeness thereby. Leydig mentioned as early 

 as 1876 the spongy structure of the red blood corpuscles of 

 Triton : " Here also there passes out from the nucleus, in radial 

 distribution, a fine network of threads towards the periphery of 

 the cell." The figure of the network, which he depicted in 1885 

 within the blood corpuscles, is, however, much too coarse, and can 

 scarcely represent the true network. 



Frommann also observed, as far back as 1880, a reticulate 

 structure in the red blood cells of Salamandra maculosa, but was 

 of opinion that the protoplasm of the blood corpuscles was 

 originally quite homogeneous, and only became differentiated into 

 a network under the influence of an induction current applied 

 to it. 



