18 SUPRARENAL GLANDS. 



to write in a vertical position, and it records the seconds in steplike 

 groups so that they can be counted off at a glance. 



A very convenient manometer is the ordinary one of glass made 

 into the form of a U . The internal diameter should be as near as pos- 

 sible to 4 mm., as at this width the least error occurs. a To the hori- 

 zontal portion of the tube a small right-angular tube is sealed, and 

 this is connected with the pressure bottle. At the end of the hori- 

 zontal portion a small flexible lead tube is connected by means of 

 thick- walled rubber tubing, and the opposite end of the lead tube 

 connects with a wash-out cannula. 



The most convenient form of wash-out cannula is the one which has 

 been used in Professor Howell's laboratory for ten or fifteen years and 

 consists of a metallic T tube. The long arm of the T is divided in its 

 lower half by a longitudinal partition, which separates this part of the 

 tube into two sections, one continuing on through the full length, the 

 other communicating with the side arm of the T. 6 When this tube 

 is inserted into the glass cannula and connected with the carotid artery 

 a continuous stream of fluid will wash out any clots which may form. 



In recording respiration the writer uses, when necessary, the chest 

 tambour connected with an ordinary Marey tambour, writing directly 

 upon the drum of the kymograph. The secret of obtaining good 

 respiratory tracings lies in the use of extremely thin rubber. For 

 this purpose rubber about as thin as tissue paper is best. For accu- 

 racy in reading pressures, a running base line is used. In commercial 

 work where it is necessary to save time, the paper is further divided 

 by a series of equidistant lines running parallel to the base line to 

 facilitate reading off measurements. One adjusted to run at the level 

 of normal pressure is especially desirable for rapid work. 



As to the respiration apparatus, at present the most suitable one 

 seems to be that of Meyer c because of the alternate force and suction 

 pumps, but that of Hoyt, d which is merely a force pump, is very 

 serviceable. 



Preparation of animals for testing. — The animal should be carefully 

 anaesthetized both for humanitarian reasons and to render it motion- 

 less, as any motion on the part of the animal would vitiate the results. 

 If necessary, curare with morphin may be used to secure immobility ; 

 then artificial respiration will be required. While the use of chlore- 



a Schaefer, E. A. Textbook of Physiology, vol. 2, p. 78. 



b Hermann, L. Exper. Pharmacology, 1883, p. 101. 



c Meyer, H. Zwei neue Laboratoriumsapparate. Arch. f. Exp. Path. u. Pharmakol., 



vol. 47, p. 426, 1902. 

 ^Hoyt, J. T. Apparatus for artificial respiration. Jour. Physiol., vol. 27, p. 48, 



1901. 



112 



