INJECTION OF THE VARIOUS VESSELS. 147 



the peripheral end of the enlargement which prevent the flow of 

 blood in this dii*ection. Make a V-shaped incision in the vein cen- 

 trad of the valves in the same manner as directed for the artery 

 (§ 356). Compress the thorax and liold tlie cat upright to facilitate 

 the flow of blood. 



When as much blood as possible is removed, insert the canula 

 (Fig, 42), and inject plaster prepared as directed (§ 359). 



The injection should be made as dii'ected for the arteries, but it 

 should be remembered that the walls of the veins are thinner than 

 those of the arteries, and hence the pressure must be more moderate. 



On account of the valves in the systemic veins (Fig. 102), it is necessary to inject cen- 

 trad. The injection may be made to pass the valves sometimes, however, by manipulating 

 the part while the mass is forced in. 



§ 363. Injection of the Aorta Abdominalis. — Posture and 

 Exposure. — Place the cat dorsicumbent, and then expose the ab- 

 dominal viscera as shown in Fig. 79, and directed hereafter. 



Turn the four flaps aside, and then turn the intestines to the left. 

 The right kidney will be seen on the right side, and in the middle 

 line the postcava (Fig. 101). 



§ 364. Dissection, and Insertion of Canula. — With the tracer 

 tear away the mesentery (Fig. 80) and connective tissue in the middle 

 line opposite the caudal margin of tlie right kidney. The aorta is 

 dorsad and smistrad of the postcava in this region, and between 

 the two great psoas muscles. Free it for 2-3 cm. Make a Y-shaped 

 incision with scissors (Fig. 40), insert and fasten the canula, and 

 inject as directed above (§ 359). 



If only the cephalic part of the body is to be studied, it is necessary to inject cephalad 

 only, but if the entire animal is to be studied, one should inject first cephalad and then 

 caudad. The second injection should be made as soon as possible after the first. 



As soon as the injection is made, the postcava should be opened to allow the blood to 

 escape. 



§ 365. Injection of the Postcava. — The exposure is the same as 

 for the Aorta abdominalis. Inject as du-ected for the Y. femoralis 

 (§ 362). 



§ 366. Injection of the V. Jugularis Externa. — Posture. — Place 

 the cat dorsicumbent and a block flatwise under the neck and 

 shoulders. Rotate the head so that the nose points away from the 

 side to be injected. 



Exposure. — Press upon the throat and find the larynx (Fig. 30, 



