236 TWO IMPORTANT 



later than from five to ten minutes after the blood had been shed. 



Dr. Freund's experiments showed that if the interior of a 

 glass vessel were smeared with vaseline, and blood received into 

 it through a greased cannula in direct communication with the 

 artery of an animal, he could, by covering the blood so obtained, 

 with a layer of liquid paraffin, keep it from coagulating for several 

 hours. Prof Haycraft also succeeded in keeping the blood fluid 

 by pouring into a venous capsule containing some blood a mixture 

 of vaseline and paraffin, and shaking this mixture from time to 

 time with the blood. The blood-globules were thus isolated by 

 the paraffin from contact with the wall of the blood-vessel, and 

 under these circumstances remained fluid for some hours. 



The life of leucocytes under the same conditions could not be 

 prolonged indefinitely, as these amoeba-like organisms are deprived 

 of their natural supply both of oxygen and nourishment. What 

 chemical changes in the corpuscles (or metabolism) lead to the 

 production of fibrine we do not yet know, any more than we 

 know how any of the organic ferments of various cells of the 

 body are produced. 



The earliest tribal history of the white blood-corpuscles, which 

 play so wonderful a part in the life history of animals, may be 

 guessed at from the individual history of certain flagellate organ- 

 isms, in which some of the amoeba-hke cells set up currents of 

 water with their cilia, and others simply ingest the food directed 

 towards them by the ciliated cells. These feeding cells, which 

 after a time immigrate into the interior of the flagellate colony, 

 appear to be the prototypes of the white blood-corpuscles of the 

 higher animals. In a later stage of the tribal history of leucocytes, 

 they form the permanent internal layer (endoderm), or feeding 

 cells, in animals as low in the state of life as hydra, and of all 

 animals above the protozoa, in their gastrula stage. A profoundly 

 interesting account, by Prof Metschnikoff, of this theory will be 

 found in the American Naturalist, for May, 1887, and the illus- 

 trations demonstrate the gradual advance from the flagellate colony 

 of Protospongia to the Gastrula type. 



The second series of experiments deals with a very different 

 class of phenomena to that of the first— namely, the part taken by 



