XVi PROCEEDINGS OF THE 



The following communications were made : — 



(1) Dr Batty Shaw showed a man in whom an acromio-trachelian 

 muscle (levator claviculse) was remarkably well developed on the left 

 side. The last specimen shown at the Society was also developed on 

 the left side of the neck of a woman. It was suggested that this 

 muscle occurs much more frequently on the left than on the right 

 side. 



(2) 2I remarkable condition in a Rabbit simulating the occurrence of a 

 Double Heart. By Professor Arthur Thomson. 



The specimen exhibited was removed from a half-bred Belgian 

 hare, aged 10 months, and was sent to me under the impression that 

 the case was an instance of the occurrence of a double heart. Un- 

 fortunately I did not receive the entire animal, but only the thoracic 

 portion of the trunk ; and owing to the fact that the neck had been 

 severed and the diaphragm much cut, the connections and relations 

 of the various parts were disturbed. 



So far as could be ascertained, the natural position of the anomalous 

 organs is that represented in fig. 1. As will be seen from the draw- 

 ing, there are what look like two hearts, placed one above the other, 

 or, more correctly speaking, one in front of the other ; both these 

 organs seem to have been lodged within the same pericardial sac. 

 The upper of the two (using this expression in relation to its position 

 as displayed in the figure) was, in respect of structure, a normal 

 heart, possessing two auricles and two ventricles, with associated 

 valves and vessels. 



In one respect only could this heart be considered as abnormal, 

 and that was in reference to the veins draining into the right auricle. 

 No trace of a right anterior vena cava could be found either in the 

 superior mediastinum or in the immediate vicinity of the auricle, and 

 there was certainly no corresponding opening into the auricular 

 cavity. The left anterior cava, marked c, fig. 1, though apparently 

 the only vessel draining the blood from the head and upper hmbs, 

 was of small size, and in place of opening directly into the right 

 auricle, joined the posterior vena cava prior to its entrance into the 

 heart. 



As shown in fig. 1, the upper (anterior) heart seemed to rest on the 

 accessory organ which intervened between it and the diaphragm. 

 This anomalous structure was about the size and consistence of the 

 left ventricle of the normal heart. Its connections and relations 

 may best be understood by an examination of fig. 2, in which the 

 two so-called hearts are seen drawn apart and turned aside to the 

 left. Here the accessory organ is seen to be affixed to the side of the 

 posterior vena cava, just where it pierces the tendon of the diaphragm, 

 the length of vein intervening between the two hearts being 23 mm. 

 In this figure the posterior vena cava is the only vessel seen opening 

 into the right auricle, though to the left of it a slender fibrous band, 

 which I take to be a remnant of the left omphalo-meseraic vein, 



