398 



Mr. F. Galton's Experiments in Pangenesis. [Mar, 30, 



I calculate the change of blood effected by transfusion, or by cross-cir- 

 culation, upon moderate suppositions as to the three following matters : — 



(1) The quantity of blood in a rabbit of known weight. 



(2) The time which elapses before each unit of incoming blood is well 

 mixed up with that already in the animal's body. 



(3) The time occupied by the flow, through either carotid, of a volume of 

 blood equal to the whole contents of the circulation. 



As regards 1, the quantity of blood in an animal's body does not ad- 

 mit, by any known method, of being accurately determined. I am content 

 to take the modern rough estimate, that it amounts to one-tenth of its total 

 weight. If any should consider this too little, and prefer the largest 

 estimate, viz. that in Valentin's 'Repertorium,' vol. in. (1838), p. 281, where 

 it is given for a rabbit as one part in every 6' 2 of the entire weight, he will 

 find the part of my argument which is based on transfusion to be weakened, 

 but not overthrown, while that which relies on cross-circulation is not 

 sensibly affected. 



As regards 2, the actual conditions are exceedingly complex ; but we 

 may evade their difficulty by adopting a limiting value. It is clear that 

 when only a brief interval elapses before each unit of newly infused blood 

 is mixed with that already in circulation, the quality of the blood which, at 

 the moment of infusion into one of the cut ends of the artery or vein, is 

 flowing out of the other, will be more alienized than if the interval were 

 longer. It follows that the blood of the two animals will intermix more 

 slowly when the interval is brief than when it is long. Now I propose to 

 adopt an extreme supposition, and to consider them to mix instantaneously. 

 The results I shall thereby obtain will necessarily be less favourable to 

 change than the reality, and will protect me from the charge of exaggera- 

 ting the completeness of intermixture. 



As regards 3, I estimate the flow of blood through either carotid to be 

 such that the volume which passes through it in ten minutes equals the 

 whole volume of blood in the body. This is a liberal estimate ; but I could 

 afford to make it twice or even thrice as liberal, without prejudice to my 

 conclusions. 



Upon the foregoing data the following Table has been constructed. The 

 formulae are : — Let the blood in the Silver-grey be called a, and let its 

 volume be V, and let the quantity u of alien blood be thrown in at each 

 injection, then the quantity of blood a remaining in the Silver-grey's circu- 

 lation, after n injections, 



If the successive injections be numerous and small, so as to be equivalent 



to a continuous flow, then, after w of alien blood has passed in, the for- 



w 



mula becomes Y.e V. 



