G. GENERAL NATURAL HISTORY AND ZOOLOGY. 319 



these experiments they ascertained that there was one half 

 per cent, of hydrogen in venous blood, but none in arterial. 

 Outside heat was found to have a great influence upon the 

 oxygen of the arterial blood, its amount being much dimin- 

 ished after exposure to a high external temperature, although 

 the number of respirations per minute is raised thereby. It 

 would seem that increasing temperature decreases the en- 

 dosmotic interchange of gases through the pulmonary mu- 

 cous membrane, which has a greater influence in determining 

 the amount of oxygen in arterial blood than the opposing fact 

 of increased respiration. The lowering of the temperature 

 was accompanied by an augmentation of carbonic acid. The 

 amount of oxygen was dependent upon the activity of respira- 

 tion, the increase of bodily temperature being at first followed 

 by a decrease, and soon after it an increase of carbonic acid 

 in the venous blood. Oxygenation takes place in the capilla- 

 ries, and not in the larger vessels. 



In death from cold there is a decrease in the consumption 

 of oxygen, and but little difference in the composition of the 

 arterial and venous blood. In death from heat there is, how- 

 ever, an enormous consumption of oxygen, and eventually 

 the venous blood contains but little of the gas. The mus- 

 cles become very acid, which was the cause of their speedy 

 and pronounced post-mortem rigidity. 21 A, August 21, 

 1874, 809. 



THE PIGMENT SCALES OF THE BLOOD. 



Dr. J. G. Richardson makes an interesting suggestion as to 

 the origin and nature of the so-called "pigment scales or 

 flakes" of the blood. He says : "I call attention to an egre- 

 gious error, by which several microscopists of acknowledged 

 ability have been ensnared, namely, a belief in the impor- 

 tance of the ' pigment cells ' or ' scales ' described by Frerichs, 

 of Berlin, as occurring in the blood; of similar bodies found 

 by Drs. Meigs and Pepper, of this city, under like circum- 

 stances ; and of the pigmentary particles, or celluloids, fig- 

 ured by Dr. William Roberts, of Manchester, England all of 

 which I assert to be simply and solely accumulations of dirt 

 (especially the remains of red blood corpuscles) in the little 

 excavations or slides in ordinary use." 



Dr. Roberts observes : " I have been in the habit of ob- 



