BIOLOGY. 299 



than the taste or caprice of man. We must, therefore, be very 

 careful in ajiplying to man the principles of zootechny. — Reader. 



« 



COLOR OF MAN. 



Dr. John Davy read a paper on this subject, before the British 

 Association, in 1866. 



After enumerating the varieties of color of the human races, 

 and their connection with latitude and climate, he considered the 

 probable causes to which the difference of color may be referred. 

 Of these he placed first, exposure to tlie sun's rays ; it being an 

 established fact, expressed in ordinary term by " sun-burn," that 

 the sun's rays acting on the skin have a darkening effect ; next, 

 warmth of climate and an average high temperatui-e throughout 

 the year, under the influence of which there appears to be a ten- 

 dency to accumulation of carbon in the system, as indicated by 

 the little difference of color of the arterial and venous blood under 

 exposure to a high temperature. An explanation of certain ex- 

 ceptional instances was next offered ; as of the darker hue of the 

 Esquimaux, to exposure to the sun's i-ays during that portion of 

 the year that the sun in the Arctic regions is constantly above the 

 horizon ; and during the other portion, their winter, to their living 

 shut up in a close impui-e air, and to their food being chiefly of a 

 kind abounding in carbon and hydrogen ; or, taking an opposite 

 instance, as that of mountaineers, who, though much exposed to 

 the sun, are commonly ftiirer than the latitude they inhabit would 

 seem to warrant, to their blood being better aerated from the 

 purer air inhaled and the active exercise they take, producing an 

 accelerated action of the heart, and a more rapid flow and cfrcu- 

 lation of the blood. Further, he adverted to hereditariness on 

 atavism, as deserving of attention in considering the color of 

 races, and more especially its importance as to the great question 

 of unity or difterence of races ab origine ; for, if climate should 

 be found to have greater effect than blood in modifying color, 

 unity might be infen-ed, and vice versa. In conclusion, he dwelt 

 on the connection of good color and a fine complexion Mdth 

 health, to which nothing can contribute more than pure air, and 

 exercise in the open air. 



PHENOMENA OF FREEZING IN ANIMALS. 



The following are the results of a long series of experiments by 

 M. Pouchet, in reducing the bodies of animals to the temperature 

 at which freezing takes place. 1. The first phenomenon produced 

 by cold is a contraction of the capillaries to the degree that a blood 

 globule cannot enter. 2. The blood globules are completely dis- 

 organized. 3. Every completely frozen animal is entirely dead, 

 and cannot be reanimated. 4. When only a part is frozen, it is 

 destroyed by gangrene. 5. If the part frozen be not extensive, 

 and only a few disorganized blood globules pass into the circula- 

 tion, the animal may recover. 6. If, however, the part frozen be 

 of considerable extent, the mass of altered globules thrown into 



