22 



Scientific Proceedings (25). 



utes. When the traction is removed, there is again a latent period 

 of several seconds, and then the pressure assumes its original level. 

 Up to a certain point, the extent of the fall varies with the force 

 of the traction ; in most animals the maximal fall is reached when 

 a weight of about 200 gm. is suspended from the divided carotid 

 artery. A larger weight causes dyspneic convulsive respiration 

 and may raise the blood pressure, probably by vaso-constriction. 



The reflex is fairly resistant to most forms of shock. It oc- 

 curs after curare, atropin, suprarenal, strychynin and phenol, and 

 during depressor, splanchnic, and accelerator stimulation. When 

 moderate doses of nicotin are injected, it is temporarily abolished, 

 but reappears in a few minutes, whilst the vagus ganglia are still 

 paralysed. This phenomenon can be reproduced by repeating the 

 nicotin treatment. 



11 (267) 



A modification of Teichmann's method for obtaining hemin 

 crystals, with a demonstration of specimens. 



By JAMES P. ATKINSON and ARTHUR I. KENDALL. 



[From the Chemical Laboratory, Department of Health, 

 City of New York.~\ 



This modification consists in heating suspected blood in a 

 tightly plugged or sealed tube. Heating is best carried out by 

 immersing the tube in boiling water. The reagents are those 

 usually employed, i. e., sodium chloride and glacial acetic acid. 

 Heating is continued for fifteen minutes, at the end of which time 

 the tubes are removed from the water bath and allowed to cool 

 slowly at room temperature. After cooling, the tubes are broken 

 open and the liquid poured into a watch glass or small evaporation 

 dish and concentrated over the water bath. When the volume of 

 the liquid has thus been reduced to a few drops, it is poured on a 

 glass slide and covered with a cover glass. If sodium chloride 

 crystals appear under the microscope a drop of water will dissolve 

 them and leave the observation of the hemin crystals unobstructed. 

 The treatment with the hot glacial acetic acid in the closed tube 

 completely decolorizes the material on which the stain occurs. 

 Heating in the closed tube keeps the condition of temperature and 



