PRELIMINARY OPERATIONS 99 



needed this method is of but little use. If the animal be 

 kept under the influence of a hypnotic such as chloretone, 

 then it may be of some use. It is best, however, that the 

 method be avoided, at least ~by students. Cushny has de- 

 vised a special apparatus for recording respiration where 

 greater accuracy is required. The apparatus consists of 

 a long narrow box with one-half or more of the ends (up- 

 per part) removed. The box can be turned bottom up- 

 wards over the animal as it lies on the operating table. A 

 very thin flexible rubber membrane is stretched loosely in- 

 side the box, being attached (air tight) to the sides and ends. 

 The bottom of the box (now turned upward) thus forms a 

 closed cavity over the entire chest and abdomen of the 

 animal (rabbit). "When the animal inspires the rubber 

 membrane will be lifted up and the air in the upper 

 part of the box will be driven out through a tube to the 

 recording tambour. Another tube in the box carries a 

 short rubber tube and a screw clamp. This serves as an 

 adjustable by-pass for the excess air if the tambour is too 

 small to record all changes (as are all tambours now on 

 the market). A small spirometer may also be used to re- 

 cord the respiratory movement by this method. (See also 

 Cushny and Lieb, Journal of Pharmacology and Experi- 

 mental Therapeutics, 1915, vi, 451.) 



Another method of recording respiration consists in at- 

 taching a string to the tip of the ensiform (Xiphoid) car- 

 tilage by means of a pin hook. The string passes over 

 pulleys to a lever (or to two connected tambours) which 

 writes on the drum. 



(h) Beginning of the Records. Take the bull-dog off 

 the carotid artery if this has not been done before and ob- 

 serve the blood-pressure tracing on the drum. Adjust the 

 pointer and also the respiratory tambour if it is not al- 

 ready making a satisfactory record. Do not proceed with 

 the experiment until a perfectly satisfactory record is be- 



