108 Dr. J. A. McWilliam. The Structure and Rhythm [Jan. 29, 



glacier in which unusually powerful forces may be supposed to be at 

 work. Moseley's argument, however, seems to be decisive against the 

 belief that the ordinary comparatively undisturbed descent of a 

 glacier along a moderately sloping bed takes place by fracture and 

 regulation. Moseley's value of the shearing strength of ice, which 

 has been shown to be enormously too great as a measure of the re- 

 sistance of ice to slow shearing, would appear on the other hand to be 

 an inferior limit to the resistance to the shearing fracture which must 

 precede regelation. Moseley has at any rate done good service by 

 calling attention to the comparatively small intensity of the shearing 

 force of gravity in the ordinary descent of a glacier. It would hardly 

 have occurred to one fresh from the study of Forbes to look for 

 evidence of the viscosity of ice in hand specimens exposed to mode- 

 rate shearing forces in a laboratory. 



II. " On the Structure and Rhythm of the Heart in Fishes, 

 with especial reference to the Heart of the Eel." By 

 J. A. McWilliam, M.D., Demonstrator of Physiology in 

 University College, London. (From the Physiological 

 Laboratory, University College, London.) Communicated 

 by Professor Schafer, F.R.S. Received January 14, 

 1885. 



I. On the General Arrangement and Structure of the EeVs Heart. 



The pulsation of the eel's heart can easily be seen externally on the 

 ventral surface of the body a short way behind the pectoral fins. 

 There are no rigid structures of any kind between the integument 

 and the heart. When the very tough and resistant skin is cut through 

 and the great lateral muscles are separated from each other, the peri- 

 cardium is seen, loosely adherent to the surrounding tissues. The 

 pericardial cavity being laid open, the various parts of the heart, 

 abundantly lubricated with fluid, come into view. The organ is not 

 freely suspended in the pericardial chamber, but is attached to the 

 walls of that chamber by numerous and considerable bands, which 

 vary in size and arrangement. The bands connected with the 

 ventricle pass chiefly to the lateral and dorsal aspects of that part ; 

 they generally communicate with one another, forming a plexiform 

 arrangement, and they tend materially to restrict the locomotion of 

 the organ during systole. These bands are for the most part fibrous ; 

 they convey, however, large blood-vessels to the ventricle. These 

 blood-vessels come from the dorsal part of the pericardial chamber 

 and climb up in the fibrous bands on to the moving ventricle to 



