110 MANUAL OF HISTOLOGY. 



which, at the same time, undergoes neither a considerable variation in 

 volume nor loss of its colouring matter. It may he roughly stated to he 

 composed of a soft gelatinous substance which swells up in an excess of 

 water. 



Besides these matters which act on the cell in the manner just 

 described, we are acquainted with a number of others in which the 

 protein matters of the blood-cell are dissolved, and with them the whole 

 structure. To these belong many of the mineral acids, and the salts which 

 the alkalies form with the bile acids. The action of another series of 

 reagents consists in coagulating the albuminous matters of the blood-cor- 

 puscles ; alcohol, tannic, and chromic acid, kreasote, and certain metallic 

 salts, may be mentioned among these. 



Now, as to the effect of gases on the shape of the blood-cell, oxygen is 

 said to have the same power of diminishing its size possessed by saturated 

 solutions, while carbonic acid gas has the contrary effect. 



An elevated temperature is also said to diminish the bulk of blood- 

 corpuscles. But besides these changes already long known, we have come 

 to the knowledge of many others of great interest within the last few years. 

 If the blood-corpuscles be left to themselves in defibrinated blood, they 

 pass gradually, in losing their vitality, from the disk-shaped to the 

 spherical figure. At a low temperature many days may elapse before 

 this transition is completed. 



An electric discharge causes the cells to assume a rugged appearance, 

 coarsely granular at first, but finer later on. Soon after the corpuscle 

 takes on again the form of a smooth spheroid, and finally loses its colour 

 (Rollett). 



If a living blood-cell be warmed up to about 52 C., a wonderful change 

 comes over it (fig. 112); it becomes rapidly marked by a varying number 

 of deep indentations ; shortly after this the formation of a series of bud- 

 like processes takes place, which either separate at once, or remain for a 

 time in connection with the rest of the cell-body by means of slender 

 filiform styles (a). 



Owing to this, the most singular appearance of beaded rods is produced ; 

 globules are found with caudal appendages, &c., 

 while the portions which have become free imme- 

 diately engage in the most lively molecular motion 

 (Bvale, Schultze). 



By none of these modes of treatment are we 

 enabled conclusively to demonstrate the presence 

 of a membrane on the blood-cell of adult human 

 beings ; besides which, the changes just mentioned, 

 produced on them by an elevation of temperature, 

 can hardly be reconciled with the supposition of 

 such a structure. We are likewise never able to 



Fig. ii2.-Hu?an blood- recognise any of those phenomena of vital cpn- 

 corpuscies heated up to 52 tractility in the mature blood-corpuscle, which 



appear in so many other cells of the system. 



Attention has bee a rather recently directed to some interesting dif- 

 ferences between the blood-cells of different regions of the circulatory 

 system. According to Lehmann's discoveries, the blood of the vena 

 porta contains the ordinary so mutable corpuscles, whilst in that of 

 the hepatic vein cells of anomalous constitution are to be found ; these 

 are smaller, more swollen, approaching the spheroid form, and having 



