284 ANNUAL RECORD OF SCIENCE AND INDUSTRY, 



gradually acquired in the struggle for existence, and one 

 which must increase from the very fact that by protective 

 coloring, mimicry, etc., the persecuted species escapes the 

 less sharp-sighted pursuer. This ever-increasing sensitiveness 

 and sharp-sightedness of the pursuer on the one hand explains 

 the wonderful completeness of many natural imitations, and 

 on the other makes the acceptation of an originally very 

 slio-ht resemblance the less hazardous." American Natural- 

 ist^ September. 



COXVEKSION OF ARTERIAL INTO VENOUS BLOOD. 



A method has been proposed by Schiitzenberger for exhib- 

 iting the conversion of arterial into venous blood, by the 

 deoxidation of the former by means of the absorptive power 

 of yeast for oxygen. Thus if blood, inclosed in a thin mem- 

 brane, be immersed in water mixed with yeast, and the whole 

 exposed to a temperature of 95, it will become venous in the 

 course of an hour. By shaking it with air it will reabsorb 

 oxygen, and be reconverted into arterial blood. An appara- 

 tus has been perfected upon the above principle, from which 

 red arterial blood passed into it flows out as black venous 

 blood, and is then again saturated with oxygen, and passed 

 back into the apparatus. 8 (7, January V, 1875, 12. 



DO ACIDS COAGULATE THE BLOOD? 



. M. Ore, inquiring whether or not acids coagulate the blood, 

 has tried a number of curious experiments by means of sub- 

 cutaneous injections. On several different occasions he in- 

 jected into the veins of a dog quantities of dilute acetic acid, 

 containing from six to twenty-five grammes of the substance 

 itself. The treatment seemed in each case to be wholly in- 

 nocuous, and no coagulation occurred. Two and a half 

 grammes of sulphuric acid, diluted with sixty of water, in- 

 jected into another dog, caused a brief panting, but no other 

 perceptible effect. Four days later the creature was killed, 

 but no traces of coagulation were any where to be detected 

 in it. Somewhat similar results were furnished by the injec- 

 tion into various dogs of nitric, phosphoric, and chlorhydric 

 acids, and also of alcohol. These substances, mingled with 

 blood in free contact with the air, all cause coagulation ; but 

 in the veins no such effect is produced. 6 B^ 1875, Nov. 8. 



