CHEMICAL PHENOMENA OF RESPIRATION. 325 



To these researches must be added those of Manasse*in, as 

 to the dimensions of the red globules of the blood under 

 different circumstances. Manassein has recognized the fact 

 that the dimensions of the red globules are least, when, from 

 a pathological increase of activity, these globules are in a 

 condition to yield an exaggerated amount of oxygen (as in 

 fever), or in any condition which increases the difficulty of 

 absorption (as when under the influence of carbonic acid and 

 morphine) ; on the other hand, they increase in size when- 

 ever they are brought in contact with any medium which 

 contains a larger amount of oxygen, or are placed under any 

 circumstances which tend to check the loss of oxygen (as 

 when under the influence of refrigerants, quinine, alcohol, 

 hydrocyanic acid). 1 



The blood acting as the vehicle of the oxygen, the more 

 blood an animal possesses, the larger reserve of oxygen it 

 will have in its circulating reservoir, and, consequently, will 

 longer be capable of supporting the privation of air; thus, 

 an animal which has lost a large quantity of blood cannot 

 long exist without constant renewal of oxygen, owing to the 

 fact that, in losing the globules of the blood, it has lost the 

 oxygen which was stored up in them. The power of resist- 

 ance to suffocation exhibited by some animals has long 

 seemed inexplicable : in the case of the diving animals, how- 

 ever, Paul Bert has shown that this power is simply owing 

 to their possessing a larger quantity of blood : thus a duck 

 possesses one-third, or even one-half more blood than a land 

 fowl of the same weight ; if the latter be immersed in water 

 (or strangled), it dies in two or three minutes, while the 

 former will hold out for seven or eight minutes. This power 

 of supporting the privation of air is due to the large quantity 

 of blood possessed by the animal, which forms a sort of 

 storehouse of oxygen in combination (P. Bert, op. cit.) 



3. Function of the Pulmonary Surface. The blood, 

 which may be considered as the intermedium between the 

 tissues and the respirable medium, may be also the seat of 

 gaseous exchanges over the whole surface which comes in 

 contact with this medium. Thus, in the frog, respiration takes 

 place by means of the surface of the skin as well as by the 

 mucous surface of the lungs. If the mesentery of a batrachian 

 be stretched out, and the circulation examined, the contents 



1 See an -excellent epitome of Manasse'in's researches, by E. 

 Lauth, in u Gazette Medicale de Strasbourg." ler aout, 1872. 



