1 92 HISTOLOGY 



That the shape of corpuscles in the circulating blood is not easy to observe, is shown 

 by the fact that scientists have described it in very different ways. The circulating 

 corpuscles may be seen by spreading the mesentery of an anaesthetized guinea-pig 

 across the condenser of a microscope, having it preferably in a warm room, and then 

 placing a cover glass directly over the vessels; they are examined with an immersion 

 lens. Sketches made during such observations are reproduced in Fig. 183. The 

 upper drawing shows a vessel stretched out abnormally, and the corpuscles are corre- 

 spondingly elongated; the one at the left shows the hollow of the cup toward the ob- 

 server, the others are seen in lateral view. Pre- 

 sumably normal conditions are shown in the 

 lower sketch, which includes two flat corpuscles, 

 one of which is almost biconcave, but this form 

 is exceptional. The corpuscles are very flexible, 

 bending around any obstruction, and when free, 

 again assuming their original form. They roll 

 TJr about as they flow through the vessels, and when, 



FIG. 183. RED CORPUSCLES, SKETCHED as the blood stagnates, the current in the vessels 



WHILE CIRCULATING IN THE VES- . . . , . . . 



SELS OF THE OMENTUM OF A GUINEA- is sometimes reversed, their form does not change. 



In 1903, following Weidenreich's publication, the 



writer demonstrated the circulating corpuscles to Professor Minot, who describes the 

 cup-shape as the normal form in Keibel and Mall's "Embryology"; and in 1909 they 

 were shown to Dr. Williams who was convinced that they are cup-shaped. 



A very important result of recent studies (which Schafer does not mention) is 

 the recognition that in well preserved tissues of all sorts, and with all fixatives such 

 as are relied upon to reveal the structure of other tissues, the mammalian erythro- 

 cytes are typically cup-shaped. Other forms are exceptional. In many specimens 

 the corpuscles and other tissues are irregularly shrunken, but where the tissues in 

 general are excellently preserved, the corpuscles appear as cups. The biconcave 

 discs are flattened cups. 



In examining films of fresh blood, the biconcave discs will be seen to 

 change their appearance as the objective is lowered. When sharply in 

 focus the thin central portion appears light (Fig. 184, A); but in high 

 focus the center is dark, perhaps owing to the dispersal of light by the 

 lenticular corpuscles. The biconcave shape is apparent when the corpuscle 

 is seen on edge (Fig. 184, B). The cup-shaped forms are shown in Fig. 

 184, D ; and E represents one of the innumerable shapes due to shrinkage. 

 The cups may be irregularly infolded, presenting shapes which can be 

 imitated by indenting a soft hat. If the corpuscles are placed in water 

 or a dilute solution, their haemoglobin passes out and water enters, so 

 that they are reduced to transparent membranes or shadows (Fig. 184, 

 F). Such forms are often seen in clinical examinations of urine. In 

 dense solutions, and in fresh preparations as the plasma becomes thicker 

 from evaporation, water leaves the corpuscles. They then shrink, 

 producing spiny or nodular round masses of haemoglobin, known as 

 crenated corpuscles (Fig. 184, G). A 0.6 per cent, aqueous solution of 

 common salt is said to cause the least distortion from swelling or shrinkage. 

 In life the corpuscles doubtless change their shape, responding to the 



