LECT. V. ORIGIN OF CELLS. 113 



been regarded as the morphological elements of all animal 

 tissues. 



Recently, Donne observed, by injecting milk into the 

 blood-vessels, that the globules of milk disappeared, after 

 some time, by becoming covered with an albuminous layer, 

 like a bladder ; that they then become reduced to the con- 

 dition of white globules of the blood, which, finally also 

 disappeared, being probably transformed into red globules. 

 Afterwards, all the blood re-acquired the appearance which 

 it had before the milk had been injected into it. 



The organic element seems, then, to be reduced to a 

 vesicle consisting of a layer of albumen, collected together 

 and organized around a nucleus, formed principally of a 

 fatty substance. 



I can bear testimony to an important experiment made 

 by Ascherson : it consists in putting a fatty liquid in con- 

 tact with albumen. This latter instantly coagulates, as you 

 here see. If you mix them together, and put a drop of 

 the mixture under the microscope, you will perceive a 

 group of vesicles, each formed of a granule of oil, enve- 

 loped by an albuminous membrane, in some degree coagu- 

 lated, and, it appears, like what the real adipose cell would 

 do, on the stage of the microscope. We can see this still 

 better, by putting, on a plate of glass, a drop of oil, and one 

 of albumen, and slowly bringing them in contact: it is 

 curious to observe, by the microscope, the almost instanta- 

 neous formation of a very delicate and elastic membrane, 

 which soon acquires numerous folds. Ascherson has 

 proved, that this formation, produced by albumen and oil, 

 is really of a cellular nature. By adding a little water to a 

 drop of this formation, he saw the cells swell up, and at the 

 same time some small drops of oil escaped. By using di- 

 luted acetic acid instead of water, the cellules appeared to 

 him to become so voluminous, that they burst. In oil, on 

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