158 CIRCULATING FLUIDS : 



The nuclei may be distinctly seen in young blood-corpus- 

 cles, but in tlie process of development they become smaller, 

 and, according to Schultz and Henle, as the final solution of 

 the blood-corpuscles approaches, they altogether disappear; 

 hence the metamorphosis of the nuclei is by no means sudden, 

 but progresses with the development of the blood-corpuscles. 



Burdach,^ R. Wagner,^ and Valentin^ are of opinion, that 

 as long as the blood-corpuscles cu'culate in the living body, 

 they possess no nucleus, and that this is only formed at the 

 instant that the blood-corpuscle is removed from the circulation. 

 R. Wagner found that nuclei were formed by the mere con- 

 tact of the blood-corpuscles with atmospheric air. This is a 

 further point of analogy between the nuclei and the fibrin of 

 the plasma; and if we could only succeed in observing the 

 unequivocal reappearance of a nucleus in a blood-corpuscle 

 removed from the body, and in which, on account of its ad- 

 vanced development, the nucleus had undergone solution, we 

 might then, in my opinion, consider that the change of the 

 nuclei into fibrin was sufficiently established, especially when 

 we reflect that no other constituent of the blood possesses the 

 extremely characteristic property of being retained in solution 

 in living blood, and of separating into an insoluble mass as 

 soon as the idtality of the fluid is destroyed. 



If we assume that the fibrin is formed in this manner, it 

 follows that the amount of fibrin must always stand in an in- 

 verse ratio to that of the blood-corpuscles ; and this is in reaHty 

 the case, — that whenever the activity of the metamorphosis is 

 increased, the amount of fibrin must likewise increase ; and 

 further, that whenever the blood is hindered in its circidation, 

 or its supply of oxygen is stopped or lessened, the amount of 

 fibrin must diminish. All these consequences really take 

 place. Blood that stagnates in the vessels loses fibrin, for it 

 is consumed, while no fresh supply can be formed. Menstrual 

 blood, and the blood in melsena contain no fibrin;'* and I shall 

 subsequently refer to other similar cases. 



' Physiologic, vol. 4, pp. 27 and 94. 



^ Beitriige zur vergleicheuden Physiologie des Blutes, 1838, p. 14. 

 ^ Ilandbucli der Entwickeliingsgeschiclite des Menschen, p. 296. 

 * [That the menstrual discharge does occasionally contain fibrin will be shown in 

 a future part of this work.] 



