CIRCULATORY MEDIA 1 6$ 



and its centriole. Probably no other somatic cell that is not at or near 

 a state of mitotic division shows this structure so well. Its sphere is 

 free of the granules and its centriole is plainly seen, but this speci- 

 men does not show the form ascribed to it by Haidenhain, who de- 

 scribes the central body as a double or multiple object. The special 

 forms of these cells found in the blood-forming glands will be de- 

 scribed in that part. 



The vertebrates have a blood cor- 

 puscle that is used solely for the carry- 

 ing of oxygen, and whose cytoplasm, in 

 consequence, is free of any granules and 

 is saturated with haemoglobin. In the 

 mammals this cell is so specialized that 

 it has lost its nucleus and the whole 

 content is the oxygen-carrying medium 

 lying in the plasma. These cells can be 

 seen in the various tissues in a number FIG 



Of places, Figures 72 and 362 Showing the liver of a salamander, Cryptobran- 

 good examples of them. c f MJ - Centrosome in middle. Nu- 



cleus to right. 



In the lower vertebrates these oxy- 

 gen-carrying blood cells have retained the nucleus which, however, 

 has lost much of its usual structure and appears contracted and irregu- 

 lar, as is also the nucleus about to be lost by a young, red, blood cell in 

 a mammal. 



All these red blood corpuscles show a peculiar glassy and homo- 

 geneous appearance of the cytoplasm due to the contained haemoglobin. 

 This results in a light greenish tinge during life, which appears, however, 

 to be red when seen in some quantity in ordinary light. Such cells stain 

 differently from other cells unless the haemoglobin has been entirely 

 removed, as happens in some preparations (Perenyi's fluid). Iron 

 haemotoxylin stains them a jet black, fading under extreme decolorization 

 to some dense shade of gray or green. Aniline dyes stain them brilliantly. 



The red blood corpuscles of the salamander, Diemyclylus, can be seen 

 in stained portions of the lung wall, as they develop from a somewhat 

 advanced stage to the fully matured corpuscles with their contained 

 haemoglobin. Figure 148 shows several of these stages. It also shows 

 that even after the acquisition of the most of its haemoglobin, the cor- 

 puscle may continue to divide by mitotic division. From left to right 

 in the figure are seen successively older stages, all of which are found 

 free in the capillaries. The earlier history is not well known in this 

 salamander. 



Technic. The preparation of the blood for microscopic study re- 

 quires a vast, complicated, and delicate series of processes. There are 



