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the cell necessary for its integrity is liquefied. What is this 

 constituent? To attempt to answer that question Professor Loeb 

 investigated a vast number of organic and inorganic substances to 

 find which substances would cause the formation of this membrane. 

 He wanted to find out whether any substances besides the mono- 

 basic fatty acids would cause the formation of the membrane, and 

 he found a large number that did so. A few of them are — ether, 

 chloroform, benzol, ordinary gasoline, and a large number of 

 other substances. All these substances have only one property in 

 common — that of dissolving fats. We know that the egg, and 

 that all cells in fact, contain a certain quantity of fat, and it 

 appears at least possible that the real significance of the formation 

 of this membrane is that a layer of fat, or an emulsion of fat 

 something like cod-liver oil emulsion, is liquefied at the surface of 

 the egg by an agent which causes the formation of the membrane, 

 and that the droplets of fat thus liquefied by solvents are run 

 together to form the membrane. 



In order to test this point we may compare the behaviour of 

 these eggs with certain cells which occur in our own bodies, and 

 which are almost exclusively composed of fatty materials — the 

 red blood corpuscles. Anything which will liquefy them will also 

 cause the artificial formation of a membrane in the egg. Among 

 other things which will liquefy our red blood corpuscles are — the 

 blood of any other species of animal, or extracts from the organs 

 of any other species than our own. We are not peculiar in this 

 respect, because the red blood corpuscles of any animal are lique- 

 fied by the blood or cell extracts of any species of animal other 

 than its own. It therefore suggested itself as a possibility that 

 the eggs of the sea-urchin might be fertilized, or at least that the 

 fertilization membrane might be formed, by simply acting on them 

 with the blood of another animal, and to a certain extent this was 

 found to be true. If we act upon the eggs of the sea-urchin with 

 ox blood or sheep's blood obtained at the slaughterhouse, or with 

 the blood of the first animal experimented on — a worm — in fact, 

 the blood of any sufficiently distant species of animal, it will cause 

 a small percentage of eggs to form a membrane — not more than 

 half a per cent., and then only very slowly, perhaps in half an 

 hour or an hour. This was not at all satisfactory. Some method 

 had to be found to accelerate it, and it was found. It was dis- 

 co vered_ that the eggs of the sea-urchin could be rendered sensitive 

 to foreign bloods by special treatment. So far only one such 

 method has been found, but others unquestionably will be found. 

 This one is by acting on the eggs with the rather rare salt known 

 as strontium chloride. If we act on the eggs with a weak 

 solution of this substance for about two minutes, and then place 

 them in sea water containing a mere trace of the blood of a 

 foreign animal of another species, within two minutes nearly all 

 of the eggs are fertilized. They will not be fertilized by the 

 strontium chloride alone. Treat them only with that and the 

 eggs simply die. Place them onlv in the blood and about Tialf 

 per cent, fertilize and develop. Place them first in the strontium 

 chloride and then in the blood and nearly all will be fertilized 

 and will develop. 



These facts are connected with something very important to 

 ourselves. The fact that our blood is capable of liquefying the 

 cells of another animal shows that it contains substances which 

 are capable of liquefying living cells, but it does not liquefy our 

 own cells. It seems at present that there can be only one inter- 



