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ZALIA JENCKS 



tared glass dish. At the beginning of this series of experiments, hemor- 

 rhages of from one-third to one-half of the estimated total blood volume 

 were produced. After "milking out" 20 or 30 drops a clot usually 

 formed ; this was carefully wiped off with a previously weighed piece 

 of cotton and added to the blood in the dish. Then more blood was 

 worked out of the end of the tail. The blood and vessel were weighed 

 rapidly to centigrams two or three times, if necessary until at least 

 one-third of the whole blood volume contained in the rat had been 

 removed. This method which was laborious and unsatisfactory re- 

 sulted in occasional injury to the tail accompanied in some cases by 



Fig. 1. This shows a rat held in the bottle so that the tail is exposed for 

 "milking" out blood. 



infection. Frequently a second hemorrhage was desired before the 

 wound on the tail was completely healed. Because of this soreness 

 and the possibility of infection it often became impossible to obtain 

 a sample of healthy blood for cell count and hemoglobin determination. 

 Subsequently, therefore, the method used for obtaining blood from 

 guinea pigs in serum work was adopted. 3 In this procedure blood is 

 secured directly from the jugular vein. The rat was anesthetized with 

 ether, the fur closely clipped from its neck, a slit about \ inch long made 

 in the skin, the jugular exposed, a v-shaped nick made in the vein with 



3 Thanks are due my co-worker, Dr. W. G. Karr, for his kindly suggestion as 

 to use of this method and for his assistance in the first operations. 



