262 Veterinary Medicine. 



The cannula employed in veterinary practice is a silver tube two 

 inches in length, a quarter of an inch in diameter and furnished 

 with a shield of the same metal at one end. The trochar by which 

 it is introduced is of steel or brass. To carry out Dr. Bowditch's 

 system the operator must supply himself with a syringe of a some- 

 what smaller bore and an intermediate brass piece of a size adapted 

 to fit accurately into the cannula and supplied with a stopcock. By 

 an instrument of this kind the fluid can be drawn off by means of 

 the syringe without any risk of the introduction of aerial germs 

 which always tend to induce suppuration and even a putrefactive 

 decomposition in the contained fluid. 



The point selected to operate on is, in the horse, ox or dog, in 

 front of the anterior border of the ninth rib, at its lower end or 

 close to its union with the cartilage. The point of the trochar 

 should be directed slightly upward and forward to avoid the pos- 

 sibility of injuring the diaphragm. The skin is first rendered 

 aseptic by shaving, followed by a thorough soapy wash and a free 

 use of mercuric chloride solution (1:500). It is then pricked 

 with a lancet, then drawn aside that the wounds in the skin and 

 muscles may not correspond after the cannula has been withdrawn. 

 The trochar is then pushed steadily through the intercostal space 

 till all obstruction has been overcome, when it may be concluded 

 that the pleural sac has been reached. The trochar is now with- 

 drawn and the fluid allowed to flow from the cannula until there is 

 presumably some risk of the introduction of air, \Yhen the brass 

 piece is to be applied and the remainder drawn off with the 

 syringe or aspirator. As a substitute for the aspirator a caout- 

 chouc tube, eighteen inches long, put on the cannula or needle 

 and having its lower end plunged in a solution of boric acid 

 will prevent the entrance of germs. A prob has often to be 

 introduced to prevent plugging of the cannula by floating 

 false membranes, and a new puncture in a different place 

 may be necessary. In the case of excessive accumulation 

 it is often advisable to draw it off at two operations, as recom- 

 mended in large abscess of the pleura and for the same reasons. 

 The need for such a precaution will be understood when it is 

 stated that in bad cases the chest contains as much as six or seven 

 ordinary .stable bucketfuls of the liquid. If, however, it is lim- 

 ited in amount it ma^' be all withdrawn at once. 



