78 Mr J. G. Adami, On the action of the [May 12, 



No hooks or traces of hooks were found on the introvert. 



At the base of the introvert, j ust behind the head, is a well- 

 developed collar, such as I have described in detail in Phymosoma 

 varians. 



The mouth is surrounded by a vascular lip, which at the dorsal 

 middle line is continuous with the base of the lophophor. The 

 latter is in the shape of a double horseshoe, and is composed of 

 from 70 to 80 tentacles. 



There is nothing to call for remark in the arrangement of the 

 internal organs, with the exception of the fact that there are only 

 two retractor muscles. Such an arrangement is only met with 

 elsewhere in Ph. Ruppellii from the Red Sea. The absence of 

 hooks and of any traces of them is striking, but it occurs in five 

 other species out of a total of 28 described. 



Habitat ; the Bahama Islands, Bimini lagoon. 



(3) On the action of the Papillaj^y Muscles of the Heart*. By 

 J. George Adami, M.A., M.B., Christ's College. 



From time to time during the last twenty years continental 

 observers have suggested that, in order to explain certain clinical 

 phenomena, the papillary muscles of the ventricles must be looked 

 upon as either contracting in a different manner to, or later than the 

 rest of the heart, and in this country Ringer has suggested that 

 one form of irregularity of the heart's action is due to a want of 

 synchronism between the contractions of the muscles in question 

 and the ventricular wall. On a priori grounds it would seem most 

 unlikely that the papillary muscles contracted absolutely synchro- 

 nously with the ventricular wall, for, were this the case, they 

 would apparently nullify themselves. Attached as they are by the 

 chordse tendinese passing from their apices to the edges and under- 

 surface of the flaps of the auriculo-ventricular valves their main 

 use is to aid in the complete closure of these valves, and thus to 

 prevent regurgitation of blood into the auricles when the ventri- 

 cles contract. And such is their position with relation to the 

 auriculo-ventricular orifices that did they rapidly shorten contem- 

 poraneously with the sharp beginning of the general ventricular 

 contraction, at a time, this is, when the blood pressure in the 

 ventricular chamber has not been greatly raised, in the absence of 

 such sufficient counteracting pressure upon the under surface of 

 the valves they would the rather pull the flaps of the valves apart, 

 and aid regurgitation. Yet up to the present no one has to my 



* This paper embodies the results of a research that Professor Roy and I have 

 been engaged upon conjointly during the last year. Fuller details will be found 

 in a series of articles upon the 'Heart-beat and Pulse-wave,' published in the 

 Practitioner. 



