QUANTITY OF BLOOD. 3 



vessels. The estimates of experimenters present the following wide differences : Allen- 

 Monlins, who was one of the first to study this question, estimated the quantity of blood 

 at one-twentieth the weight of the entire body. The estimate of Herbst was a little 

 higher. Hoffmann estimated the quantity at one-fifth the weight of the body. These 

 observers estimated the quantity remaining in the system after opening the vessels, bv 

 mere conjecture. Valentin was the first who attempted to overcome this difficulty by 

 experiment. For this purpose he employed the following process : He took first a small 

 quantity of blood from an animal for purposes of comparison ; then he injected into the 

 vessels a known quantity of a saline solution, and, taking another specimen of blood some 

 time after, he ascertained by evaporation the proportion of water which it contained, 

 and compared with the proportion in the first specimen. He reasoned that the excess of 

 water in the second specimen over the first would give the proportion of the water intro- 

 duced to the whole mass of blood ; and, as the entire quantity of water introduced was 

 known, the entire quantity of blood could be deduced therefrom. Suppose, for example, 

 that the excess of water in the second specimen should be one part to ten of the blood, 

 it would show that one part of water had been mixed with ten of the blood ; and, if 

 we had injected in all five ounces of water, we should have the whole quantity of blood 

 ten times that, or fifty ounces. This method, however, is open to the objection that it is 

 impossible to take note of the processes of imbibition and exhalation which are con- 

 stantly in operation. 



The following process, which is, perhaps, the one least open to sources of error, was 

 employed by Lehmann and Weber, and applied directly to the human subject, in the 

 case of two decapitated criminals : These observers estimated the blood remaining in 

 the body after decapitation, by injecting the vessels with water until it came through 

 nearly colorless. The liquid was carefully collected, evaporated to dryness, and the dry 

 residue was assumed to represent a certain quantity of blood, the proportion of dry 

 residue to a definite quantity of blood having been previously ascertained. If we could 

 be certain that only the solid matter of the blood was thus removed, such an estimate 

 would be tolerably accurate. As it is, we may consider it as approximating very nearly 

 to the truth. We quote the following account of these observations : 



" My friend, Ed. Weber, determined, with my cooperation, the weights of two crimi- 

 nals both before and after their decapitation. The quantity of blood which escaped 

 from the body was determined in the following manner : Water was injected into the 

 vessels of the trunk and head, until the fluid escaping from the veins had only a pale-red 

 or yellow color ; the quantity of the blood remaining in the body was then calculated, 

 by instituting a comparison between the solid residue of this pale-red aqueous fluid, and 

 that of the blood which first escaped. By way of illustration, I subjoin the results 

 yielded by one of the experiments. The living body of one of the criminals weighed 

 60,140 grammes (132-7 pounds), and the same body after decapitation, 54,600 grammes; 

 consequently, 5,540 grammes of blood had escaped 28-560 grammes of this blood 

 yielded 5'36 grammes of solid residue; 60'5 grammes of sanguineous water collected 

 after the injection, contained 3'724 grammes of solid substances; 6,050 grammes of the 

 sanguineous water that returned from the veins were collected, and these contained 

 37-24 grammes of solid residue, which corresponds to 1,980 grammes of blood ; conse- 

 quently, the body contained 7,520 grammes (16-59 pounds), 5,540 escaping in the ai-t of 

 decapitation, and 1,980 remaining in the body; hence, the weight of the whole Mood 

 was to that of the body nearly in the ratio of 1 : 8. The other experiment yielded a 

 precisely similar result. 



" It cannot be assumed that such experiments as these possess extreme accuracy, but 

 they appear to have the advantage of giving in this manner the minimum of the blood 

 contained in the body of an adult man ; for although some solid substances, not belong- 

 ing to the blood, may be taken up by the water from the parenchyma of the orirans per- 

 meated with capillary vessels, the excess thus obtained is so completely counteracted by 



