342 Mr. C. W. Heat on on the Function of 



reduce itself by remaining for a few days in a tube out of contact 

 with air. The cruorine was again oxidized instantaneously by 

 agitation with air. This last experiment proves that the corpus- 

 cles have the faculty of oxidizing nitrogenous materials, either 

 their own substance or else some portion of the serum with 

 which they are in contact. Hoppe-Seyler has since found* that, 

 in a rabbit killed by drowning, the blood exhibits the spectrum 

 of reduced cruorine. That the oxygen is held in combination 

 in the corpuscle by the weak force termed by Frankland " mole- 

 cular combination/' is evident from the well-known fact that 

 carbonic oxide displaces from it its own volume of oxygen. 



Now, if the oxidation of muscle is effected in the tissue itself, 

 it is clearly necessary to suppose either that the oxygen, upon the 

 stimulus of the motor nerves, leaves its combination in the cor- 

 puscle, traverses the walls of the capillary in company with the 

 outgoing stream of nutrient fluid, and only enters into new com- 

 binations when it has passed to some comparatively distant 

 muscle-fibre, or else that the corpuscle itself liquefies and passes 

 out bodily through the thin membrane with its loosely combined 

 oxygen. Both suppositions seem to me very improbable ; for, 

 as Stokes's experiment proves that the absorbed oxygen of the 

 corpuscle is capable, without any nerve-influence, of entering 

 into direct combination with the materials of the blood itself, it 

 is difficult to understand why such combination should be de- 

 ferred until the oxygen has traversed the walls of the capillary. 

 Moreover, as muscle-fibre is now known to be at any rate not 

 the only substance oxidized to produce muscular work, it is 

 plain that much of that muscular work must, upon the current 

 theory, be produced by the oxidation outside the capillary of the 

 very same substances, fat &c, which are present abundantly in- 

 side it. Why oxygen should reject fat inside the capillary and 

 oxidize it outside it is hard to imagine. 



But evidence of a more direct kind is, I think, accessible to 

 us. The tissues are undoubtedly nourished by a stream of fluid 

 which exudes from the walls of the capillaries in virtue of the 

 pressure to which the blood is subject. As the tissues disinte- 

 grate they liquefy and are carried, together with the excess of the 

 nutritive fluid, back to the blood by means of the lymphatics, 

 which take their origin in the intervascular spaces of the tissue. 

 Hence Mayer suggested that the lymph was a measure of the 

 amount of fluid exuded from the walls of the capillaries. Taking 

 the quantity of lymph from Majendie's calculation, he inferred 

 that not 1 per cent, of the blood left the blood-vessels in the 

 course of the circulation, and consequently, as all the blood re- 



* Zeitschrift fur Chem. New Series, vol. i. p. 214. 



