THE CIRCULATION OF THE BLOOD 77 



Appendix, 11); animal holder; morphine solution with hypodermic 

 syringe; chloroform or ether; tannic acid; absorbent cotton; porcelain- 

 lined trays for instruments; cotton, calipers, and rule. 



2. Preparation. The dog of medium or large size is to be pre- 

 ferred for class demonstrations, while rabbits or small dogs may 

 be used for laboratory work by students. When rabbits are used 

 anaesthetize with ether. Wlien dogs are used anaesthetize with 

 chloroform after having given i to 1 grain of morphine hypodermic- 

 ally fifteen minutes before the use of the chloroform. 



Make a litre of one-half saturated solution of tannic acid to be 

 used as an haemostatic. 



3. Operations. (1) To Induce Artificial Respiration. The open- 

 ing of the thorax causes the lungs to collapse, and if artificial respi- 

 ration were not instituted the animal would die in convulsions in a 

 few minutes. The successful induction of artificial respiration 

 involves the opening of the trachea, insertion of respiration cannula, 

 and the maintenance of respiratory movements of the lungs through 

 the use of the bellows. 



Clip the hair from the ventral surface of the neck; make a median 

 cutaneous incision; with forceps and fingers separate subcutaneous 

 tissue, fascia, and muscles over the middle of trachea, and clear one 

 to two inches of the trachea; cut a longitudinal ventral slit into the 

 trachea and insert tracheal end of respiration cannula, ligating it 

 firmly in place. 



The animal will now breathe through the cannula. When the 

 thorax is opened but not before the bellows should be attached 

 to the cannula through the medium of a rubber tube at least one 

 foot in length, and the bellows should then be brought into rhythmical 

 action, causing the lungs to fill eighteen to twenty times per minute 

 in the case of a dog (twice as fast for the rabbit). 



After the introduction of the cannula and before the bellows is 

 attached apply the anaesthetic to the distal end of the cannula. 

 When the bellows is attached the anaesthetic must, of course, be 

 applied to the intake valves of the bellows. 



(2) To Expose the Heart. After the introduction of the respiration 

 cannula, make a median incision over the sternum from anterior 

 tip to posterior end of the xiphoid appendix. Strip the skin back 

 laterally as far as the junction between the ribs and the costal carti- 

 lages. Saturate with tannic acid solution strips of absorbent cotton 

 large enough to cover all cut surfaces. 



With strong scalpel cut through the thoracic wall at the junction 

 of the first left rib with its cartilage, carrying the incision quickly 

 back along the thorax parallel to the sternum until all cartilages 

 are cut. The cut-off ends of intercostal arteries will bleed freely, 

 but this can be stopped in a moment by folding a strip of absorbent 

 cotton wet with tannic acid over the cut-off ends of the ribs. A 



fe R A * 



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UNIVERSITY 



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