180 THE LAWS OF ORGANIC 



at 45, and in a quarter of an hour blood was 

 drawn from the jugular vein, and was thought 

 " to be the darkest venous blood we had ever 

 seen."* This result was considered to support the 

 explanation, viz. that, when the temperature was 

 high, the changes of the blood in the minute ves- 

 sels were less perfect than usual ; but when the 

 temperature was low, these changes were sup- 

 posed to be more complete, accounting for the 

 very dark condition of the venous blood. The 

 dog immersed in water at 45 must have had its 

 heat materially diminished, although this import- 

 ant point was not alluded to. The blood, from 

 the medium in which the body was placed, would 

 be determined upon the internal organs, which 

 would tend to obstruct its proper oxygenation. It 

 cannot, therefore, be denied, that the difference 

 in colour between the arterial and venous fluid, 

 in every state of the system, is to be attributed to 

 its more or less perfect alterations in the lungs. 



CC. If the dog whose blood was very dark 

 had had its temperature augmented, which it 

 ought to have had according to his doctrine, 

 there would then have been a plausibility in the 

 theory ; but it must have lost several degrees of 

 heat, for the blood, in no condition of the system, 

 assumes this aspect, unless the temperature be 

 diminished, and congestion in some part of the 

 body be present. To ascertain the temperature of 



f CRAWFORD, p. 310, 



