82 STUDENTS HISTOLOGY 



columns. 2. From shrinkage they may become crenated. 3. Still 

 further shrinkage produces the chestnut -burr appearance. 4. 

 From absorption of water they may swell irregularly, obliterating 

 the concavity of one side. 5. From continuous absorption they 

 swell, forming spheres which are finally dissolved. 



Wind a twisted handkerchief tightly around the left ring-finger, 



FIG. 57. DIAGRAM OF A COLORED BLOOD-CORPUSCLE, SIDE VIEW, SHOWING THE 

 Bi -CONCAVITY. (The thickness is exaggerated.) 



A, B. Upper plane, which, in focus, gives the appearance shown at G, Fig. 56. 

 C, D. Plane giving the appearance shown at F, Fig. 56. 



prick the end with a clean needle, and squeeze a minute drop of 

 blood on a slide, add a drop of salt solution, cover, and focus 

 with H. 



Observe: 1. That considerable variation in size of the red 

 blood -corpuscles exists. 2. The color a delicate straw tint. 

 3. That the concave centers of the corpuscles which lie flat can be 

 made to appear alternately dark and light according to the focal 

 adjustment. 4. That the concavity is also demonstrated as the 

 corpuscles are turned over by the thermal currents.* 



BLOOD -PLATES 



Minute corpuscular elements in the blood, about one-fourth the 

 size of the red disks, exist in the proportion of about one of the 

 former to twenty of the latter. They are colorless ovoid disks, 

 and are regarded by Osier as an essential factor in the coagulation 

 of the blood. 



Prick the thoroughly clean finger with a needle. Over the 

 puncture place a drop of solution of osmic acid (one per cent.), and 

 squeeze out a minute drop of blood, so that, as it flows, it is covered 

 by the acid solution. This fixes the anatomical elements, provid- 

 ing against further change. The blood, as soon as drawn, must, 

 with the acid, be immediately transferred to a slide and covered. 



"The student is at this time advised to study the corpuscular elements of the blood of such 

 animals as he may be able to command. The red corpuscles of mammals (excepting the 

 camelidae) do not vary in appearance from those of man, excepting in size. Those of birds, 

 fishes, and reptiles are elliptical, with oval nuclei. Corpuscles of the blood of invertebrates are 

 not colored. 



