A MANUAL OF PHYSIOLOGY 



interchanged are capable of laying eggs. When the hens were 

 impregnated and the eggs hatched out the colour characters of the 

 resulting offspring seemed to have been influenced, not only by the 

 hen to which the ovary originally belonged, but also by the hen to 

 which it had been transferred. Grafts of the thyroid and para- 

 thyroid have also been shown to ' take.' 



In transplantation with anastomosis of bloodvessels the main 

 vessels of the engrafted organ are sutured to suitable arteries and 

 veins in the ' host/ so that the circulation is at once effective. Con- 

 sequently there is practically no limit to the size of the grafts. The 

 kidney, spleen, and even a limb, have been successfully transplanted 

 in this way from one dog to another. Segments of arteries preserved 

 in cold storage for a few days or even weeks, and even portions of 

 arteries fixed by formaldehyde, have been transplanted so as to take 

 the place of segments removed from arteries of living animals, and 

 have continued to function perfectly for long periods. Portions of 

 veins have also been used to fill up gaps in arteries. Even hetero- 

 plastic vascular grafts have been found to succeed, portions of dog's 



FIG. 447. SUTURING BLOODVESSELS. PRELIMINARY FIXATION OF ENDS OF 

 DIVIDED VESSELS (AFTER GUTHRIE). 



Three fixing ligatures are placed at equidistant points on the circumference of 

 the cut ends, each ligature being passed through corresponding points of the two 

 vessels. The ends of the vessels are approximated by drawing on the ligatures, 

 which are then tied, and the margins of the vessels sewed together by continuous 

 stitches in the intervals between the fixing ligatures, as in Fig. 449. (Carrel's 

 method.) 



arteries, e.g., grafted into a cat, and portions of rabbit's, cat's, or 

 human arteries grafted into a dog. Doubtless the favourable result 

 is largely due to the fact that the function of the large arteries is 

 mainly a passive, mechanical one, which can be discharged even by 

 a dead tube of the requisite strength, and with the smooth interior 

 presented by a dead endothelial lining (Carrel, Guthrie). 



Parabiosis. Not only may an organ or a portion of tissue from 

 one individual be engrafted on another, but two individuals may be 

 so united that a greater or smaller degree of physiological intimacy 

 is produced between them. Occasionally, as in the famous Siamese 

 twins, an anomaly of development results in such close anatomical 

 union of the circulatory and other systems that in certain respects 

 the two individuals constitute almost a single organism, and cannot 

 be separated by surgical interference. A less intimate union can 

 be established experimentally by opening the peritoneal cavities 

 of the two animals, and suturing the skin and connective tissue 

 together so as to permit of permanent communication. Pairs of 



