THE VITAL PRINCIPLE—THE BLOOD. 17 



or elliptical ; and in fishes they are larger than 

 in any of the other vertebrate classes. 



It may be observed, that besides the red 

 blood-corpuscles, pale globules present them- 

 selves under the microscope — globules of fibrin ; 

 and between these two there appears to be a 

 sort of repulsion preventing their union, and 

 thus maintaining the blood in a fluid state. 

 But when drawn from the body, the blood soon 

 coagulates, this self-repulsion ceasing, and 

 cohesion between the corpuscles taking place. 

 The red particles are composed of a substance 

 resembling fibrin, to which the term globuline 

 has been given ; they contain a red colouring 

 matter, called hamiatosine, and a certain variable 

 quantity of oxide of iron. While from the 

 fibrin of the blood the muscles and general 

 tissues of the body are formed, it would seem 

 that the red corpuscles act the part of carriers 

 of oxygen from one part of the system to 

 another, and are thereby the active agents by 

 which animal heat is kept up ; and it is 

 observable, that the greater the energy and 

 activity of the animal, the greater is the pro- 

 portion of this red matter, and also the eleva- 

 tion of the animal temperature. It is well 

 known that there are many animals of a soft or 

 gelatinous consistence, in whose structure no 

 muscles or distinct muscular fibres can be 

 detected, although they are capable of execut- 

 ing decided movements. In such cases it is 

 very probable that motion is produced by 

 changes in the state of the particles of fibrin, in 



