GENERAL CHARACTERS. 3 



the weight of the body, is too high. More recent observations have been 

 made upon the inferior animals, by various methods, which are all more or 

 less open to objection, and which it is not necessary to describe in detail ; 

 but the results of nearly all of the experiments made within the last few 

 years show a less proportion of blood than was estimated by Lehmann and 

 Weber. Kemembering that all estimates must be regarded as approxi- 

 mate, it may be assumed that in a person of ordinary adipose and mus- 

 cular development the proportion of blood to the weight of the body is 

 about one to ten. The relative quantity of blood is less in the infant than 

 in the adult and is diminished in old age. It has been found, also, in 

 observations on the inferior animals, to be greater in the male than in the 

 female. 



Prolonged abstinence from food, except when large quantities of liquid 

 are ingested, has a notable effect in diminishing the mass of blood, as indi- 

 cated by the small quantity which can be removed from the body, under this 

 condition, with impunity ; and it has been experimentally demonstrated that 

 the entire quantity of blood is considerably increased during digestion. Ber- 

 nard drew from a rabbit weighing about two and a half pounds (1,134 

 grammes), during digestion, ten and a half ounces of blood (300 grammes) 

 without producing death ; while he found that the removal of half that 

 quantity from an animal of the same size, fasting, was fatal. Wrisberg re- 

 ported a case of a female criminal, very plethoric, from whom nearly twenty- 

 one and a half pounds of blood (9,745 grammes) flowed* after decapitation. 

 As the relations of the quantity of blood to digestion are so important, it is 

 unfortunate that the conditions in this respect were not noted in the obser- 

 vations of Lehmann and Weber. It is evident that the quantity of" blood 

 in the body must be considerably increased during digestion ; but as regards 

 the extent of this increase, it is not possible to form any very definite idea. 

 It is shown only that there is a marked difference in the effects of haemor- 

 rhage in animals during digestion and fasting. 



GENERAL CHARACTERS OF THE BLOOD. 



Opacity, The opacity of the blood depends upon the fact that it is not 

 a homogeneous fluid, but is composed of two distinct elements, a clear plasma 

 and corpuscles, which are both nearly transparent but which have each a 

 different refractive power. If both of these elements had the same refrac- 

 tive power, the mixture would present no obstacle to the passage of light ; 

 but as it is, the rays, which are refracted in passing from the air to the 

 plasma, are again refracted when they enter the corpuscles, and again, when 

 they pass from the corpuscles to the plasma, so that they are lost, even in a 

 thin layer of the fluid. 



Odor, Taste, Reaction and Specific Gravity. The blood has a faint but 

 characteristic odor. This may be developed so as to be very distinct, by the 

 addition of a few drops of sulphuric acid, when an odor peculiar to the ani- 

 mal from which the blood has been taken becomes very marked. 



The taste of the blood is faintly saline, on account of the presence of a 



