the Blood in Muscular Work. 343 



quired renewal on its return to the heart, that 99 per cent, of the 

 total oxidation of the body was effected in the blood-vessels. In 

 this form, however, the proof is not quite complete. It may be 

 argued that a large proportion of oxygen leaves the blood-vessels 

 in the exudate, and that, small as is the total quantity of the 

 latter, it may yet contain enough oxygen to do the work of the 

 muscles. 



I have therefore made a calculation of the quantity of oxygen 

 which can possibly be supposed to pass out of the blood. I pur- 

 posely exaggerate every figure employed, in order if possible to 

 avoid cavil. 



The first point is to ascertain the extreme quantity of fluid 

 exuded in twenty-four hours. Bidder and Schmidt estimate the 

 lymph at 22 lb. I will take it at 30 lb. A large proportion 

 of this arises of course from glands and other organs which do 

 no muscular work; but this I neglect. It may be suggested 

 that some part of the fluid exuded may return direct to the ca- 

 pillaries without passing through the lymphatic system. No 

 doubt this is the case ; but the quantity so returned is probably 

 small, as the pressure in the vessels would naturally tend to 

 prevent it. The pressure, indeed, probably acts in forcing the 

 fluid onwards into the lymphatics. Nevertheless, to avoid ques- 

 tion, I will assume that the quantity returned in this way is 

 twice as great as the lymph, and I thus get 90 lb., or about 40 

 litres, as the daily amount of exudate ; and I think every one will 

 admit that this is an extreme overstatement. 



Any oxygen which passes out into the tissue must obviously 

 pass in solution in this 40 litres ; and the next point is to ascer- 

 tain the quantity of oxygen which it can possibly be supposed to 

 carry with it. Lymph resembles diluted liquor sanguinis in 

 composition, and is destitute of colour. The exudate is therefore 

 in all probability derived mainly from the liquor sanguinis, which, 

 as Berzelius showed, will hardly dissolve more oxygen than 

 water. Moreover, its dilution proves that, as might have been 

 anticipated from the colloidal character of blood, a considerable 

 part of the exudate actually consists of water. But, to put the 

 case in the strongest possible light, I will assume that the whole 

 of the exudate consists of liquefied corpuscles — of scarlet cruorine, 

 in fact, charged to its utmost with oxygen. Again exaggera- 

 ting, I assume that the corpuscles of arterial blood contain 40 

 per cent, by volume of oxygen. This gives as the quantity of 

 oxygen in the 40 litres of exudate 16 litres, or 22*88 grammes. 

 Is this sufficient to do the muscular work actually accomplished 

 in the twenty-four hours ? The following is an extremely low 

 estimate of the daily work of the muscles : — 



