ANATOMICAL ELEMENTS. 



This appearance is an optical effect due to the form of the corpuscles ; their 

 biconcavity rendering it impossible for the centre and edges to be exactly in 

 focus at the same instant, so that when the edges are in focus, the centre is 

 dark, and when the centre is bright, the edges are shaded. 



As the blood -corpuscles are examined with the microscope, by transmitted 

 light, they are nearly transparent and of a pale-amber color. It is only when 

 they are collected in masses that they present the red tint characteristic of 

 blood as it appears to the naked 

 eye. This yellow or amber tint is 

 quite characteristic. An idea of 

 the color may be obtained by large- 

 ly diluting blood in a test-tube and 

 holding it between the eye and the 

 light. 



In examining blood under the 

 microscope, the corpuscles are seen 

 in many different positions, and 

 this assists in the recognition of 

 their peculiar form. 



It has long been observed that 

 the blood-corpuscles have a remark- 

 able tendency to arrange them- 

 selves in rows like rouleaux of coin. 

 This appearance is due to the fol- 

 lowing conditions : 



Shortly after removal from the vessels, there exudes from the corpuscles 

 an adhesive substance which causes them to stick together. Of course the 

 tendency is to adhere by their flat surfaces (Robin). This phenomenon is 

 due to a post-mortem change ; but it occurs so soon, that it presents itself 

 in nearly every specimen of fresh blood, and is therefore mentioned in con- 

 nection with the normal characters of the blood -corpuscles. 



The diameter of the blood-corpuscles has a more than ordinary anatomi- 

 cal interest; for, varying perhaps less in size than other anatomical ele- 

 ments, they are often taken as the standard by which an idea is formed of 

 the size of other microscopic objects. The diameter usually given is ^g^o f 

 an inch (7' 17 ft). The exact measurement given by Robin is -^j of an 

 inch (7'3 /*). Very few corpuscles are to be found which vary from this 

 measurement. Kolliker, who gives their average diameter as ygVir of an 

 inch (7 /*), states that "at least ninety-five out of every hundred corpuscles 

 are of the same size." 



Measurements of the blood-corpuscles of different animals are important, 

 from the fact that it often becomes a question to determine whether a given 

 specimen of blood be from the human subject or from one of the inferior 

 animals. Comparative measurements also have an interest on account of a 

 relation which seems to exist in the animal scale between the size of the 

 blood-corpuscles and muscular activity. In all the mammalia, with the 



FIG. 2. Human red blood-corpuscles, arranged in 

 rows (Funke). 



