FOEMS OF BLOOD-CELLS. 



117 



Fig. 45. 



Fig. 40. 



Action of acetic acid on elliptic cells. 



Reptile blood-cells magnified 500 diameters. 



The mammals in which the blood corpuscles are not round, but ellip- 

 tic and bi-convex, are the camel, the dromedary, and the llama. In 

 birds and amphibia they are oval. The difference in the shape and size 

 of these cells is of the more importance, since observations and measure- 

 ments by the microscope may lead us to a correct reference of a sample 

 of blood to its origin when chemical analysis would afford us no assist- 

 ance. It is not to be forgotten, however, that both in size and form a 

 blood-cell undergoes changes according to unequal pressures Variations Q f 

 exerted upon it, or to the physical circumstances under which the form of 

 it is placed, liquid readily finding its way into its interior or blo ills ' 

 exuding therefrom according to the laws of endosmosis, the elastic sac 

 perfectly accommodating itself to these changes. As a consequence of 

 these modifications, there will, of course, follow variations of specific grav- 

 ity in the cell, differences in its tendency to sink in the plasma which 

 surrounds it, and also differences in its tint of color. 



By Mr. Wharton Jones, the colored blood-disc of the mammalian is 

 regarded as being homologous with the nucleus of the color- Human blood 

 less corpuscle of the same blood, and it may therefore be disc is a ceii^- 

 spoken of as a free cellseform nucleus, the cell itself having form nucleus - 

 deliquesced or become disintegrated, and the nucleus, filled with globulin 

 and coloring matter, remaining. 



The cell wall of the blood-cells is generally admitted to be fibrin, or 

 some substance allied thereto ; but there has been much dif- Nature of the 

 ference of opinion respecting the constitution of the nucleus cell walls and 

 of those cells which possess it. By some, this also has been 

 regarded as fibrin ; by others, as fat ; and by others, as a species of horn, 

 to which the designation of nucleine has been given. 



The cell wall of the white corpuscles does not appear to be elastic. 

 It is viscid, and hence these bodies, tend to agglutinate with one another : 



