146 



RADIOISOTOPES IN BIOLOGY AND AGRICULTURE 



ity of thrombosis or embolism (28). Detrick and Rhodes (29) have 

 described a modified injection needle that facilitates insertion of the cath- 

 eter. They have also suggested that a length of nylon fishing leader be 

 used as a stylet to prevent blood from entering and blocking the catheter 

 between periods of use. 



Catheterization has proved satisfactory with sheep, cattle, and horses; 

 the jugular vein is convenient, and a 16-gauge needle is customarily 

 employed. Pressure over the base of the neck will distend the vein and 



Fig. 4-21 . I .\iMi>ure of trachea of rat for the insertion of a hypodermic needle between 

 the rings for intratracheal administration. {Courtesy of R. W. Wagner, Biology 

 Section, Radiological Sciences Department, General Electric Company, from work per- 

 formed under AEC Contract W-il-lQ^yEng-b2.) 



make it easier to locate and pierce. Kainer and Dickson (30) have 

 pointed out that the external jugular vein of cattle has several valves that 

 interfere with venipuncture. It was recommended that the anterior 10 

 to 12 cm of the vein be employed, since this region was found to be free of 

 valves. Livestock can be adequately restrained for this procedure in 

 the regular metabolism units or stanchions. 



Procedures with swine for injection into the anterior vena cava have 

 been described by Carle and Dewhirst (31). Small animals are restrained 

 manually in a dorsal recumbent position. A 20-gauge 13-^-in. needle is 

 inserted about 2 cm on either side of the point of the cariniform cartilage 



