TWO IMPORTANT BIOLOGICAL EXPERIMENTS. 235 



and Dr. Freund show that the changes in the blood, which take 

 place during coagulation, are primarily changes of life, not death, 

 and that coagulation may be indefinitely retarded if the leucocytes 

 are prevented from coming into contact with any solid body, and 

 are kept in a soft fluid medium, such as oil. 



It will be interesting to give a detailed account of one experi- 

 ment. A finger, previously well smeared with oil, and rendered 

 turgid by a bandage, is plunged into a tube containing oil, and 

 then pricked below the surface with a needle. The blood so 

 obtained comes in contact only with the tissues of the finger in 

 the puncture, neither the surface of the skin, nor the air, nor any 

 particle of dust being permitted to contaminate it. The drops of 

 blood will begin to descend in the oil, taking from ten to fifteen 

 minutes to fall a foot. When the largest drop (which must on no 

 account be allowed to touch the glass, or the experiment will fail) 

 has nearly reached the bottom, the tube must be inverted, and the 

 drops will again begin to fall, and this process may repeatedly be 

 gone through. A drop may now be taken on a well-oiled spoon, 

 and placed on a clean glass slide. It will be found on drawing a 

 needle through the drop that it is perfectly fluid, there being an 

 entire absence of any coagulation, even in the form of the minutest 

 trace of fibrine threads. 



The finger was then withdrawn from the oil, and carefully 

 wiped, and a drop of blood, from the same puncture from which 

 blood was drawn in the first experiment, was placed on a carefully- 

 cleaned and dust-free glass slide. This slide was covered, and 

 the cover ringed with oil to keep the blood from further 

 contact with dust and air. It will be seen, however, how potent 

 were the effects of contact with the dust of the air, and with a 

 hard substance like a glass slide. The blood was immediately 

 examined, commencing at 2.55 p.m., and amoeboid movements 

 could be distinctly seen in the white blood-corpuscles, which became 

 gradually more active till, in three minutes, 2.58 p.m., fibrine 

 threads were observed to be forming. At 3.3 p.m. the white 

 corpuscles were still actively amoeboid, though the field of the 

 microscope was thickly covered with delicate fibrine threads. In 

 some cases the amoeboid movements continued for some hours, 

 though in the blood of the experimenters coagulation occurred never 



