470 



STATE BOARD OF AGRICULTURE. 



it be that this ready solubility for gasoline of the fats and lipoids of 

 insect-tissues fuiuished a means for hindering the absorption of oxygen 

 by the tissues, or lessening the oxidation of hydroquinone by the oxidase 

 of insect-tissue extract in the presence of gasoline? It seemed that such 

 might be the case, if in fact it should be found that gasoline, held in 

 solution by fats and lipoids, lessened their solubility for oxygen — and by 

 so doing, lowered the rate at which atmospheric oxygen might pass into 

 an extract, or from tlie trachaeoles (or by any path) through the fluids 

 bathing the cells, on into the cells to those agencies which (in life) 

 utilize the incoming oxygen. Accordingly plans were made to determine 

 what change the absorption of gasoline-vapor by a lipoid membrane, such 

 as a lecithin membrane (or by a fat membrane) would have upon the 

 rate at which oxygen passed through it. For the series of experiments 

 to be made in this connection, it did not seem necessary or even desirable 

 to use the fat or lipoids derived from insects. Clearly, the advantage 

 would lie in eliminating all possible variable quantities. On that account, 

 a comparatively pure fat and lipoid, each of which would be uniform and 

 easily obtained, was desired. Several preliminary quantitative absorp- 

 tions of gasoline-vapor, using definite amounts (3 grams) of lard, lan- 

 olin, lecithin, cholesterin, and (for comparison) egg-yolk and egg-albu- 

 men were first carried out. Some representative results of a few of 

 these absorption tests are given in Table VI. The apparatus used was 

 that represented by Fig. Ill, except that the hooked U-tube "u" and 

 the burette ''b" were not needed. The 3-gram quantity of lecithin (or 

 eggwhite, etc.) Avas placed in a standard stender dish — so that the same 

 absorbing-surface was exposed always — and the dish was then floated 

 upon mercury in the gas-container "g. c." Most of the tests were made 

 over rather short periods, during which the barometer and thermometer 

 remained practically constant. Checks showed that in pure air the 

 volume of gas enclosed with the absorbent (fat, etc.) which was being 

 tested remained unchanged over similar periods of time. In the tests, 

 a loss in volume as shown by the gas-burette was therefore the measure 

 of the "gasoline-vapor' that had been absorbed. At the end of each test 

 the percentage of gasoline-vapor still present was determined from a 

 sample taken from the gas-container — using the '"Nordhausen sulphuric 

 acid" method of estimation alreadv described in the former bulletin. 



The lecithin (H. P. from egg, Merck) was used, as received from Merck, 

 in the form of a paste ; and in the case of cholesterin the soft dry jjowder 



