432 Proceedings of the "Royal Society of Edinburgh. 



3. On the Fossil Fishes of the Old Red Sandstone of Ork- 



ney. By Dr Traill. 



4. Mr Milne made a verbal communication respecting Instru- 



ments for registering Shocks of Earthquakes. 



1841, January 4. — Dr Abercrombie, V.P. in the Chair. 

 The following Communication was read : — 



1. On certain Physiological Inferences which may be drawn 

 from the study of the Nerves of the Eyeball. By Dr 

 Alison. Part Second. 



January 18. — The Right Hon. Lord Greenock, V.P. in the 

 Chair. The following Communications were read : — 



1. On the Mode in which Musket-balls and other Foreign Bo- 

 dies become enclosed in the Ivory of the Tusk of the Ele- 

 phant. By John Goodsir, Esq. Communicated by Pro- 

 fessor Syme. 



The author commenced by stating-, that " in all the specimens 

 lie had examined, two circumstances were at once detected ; first, 

 That the balls were enclosed, not in the true ivory, but in an ab- 

 normal structure ; and secondly, that the holes by which the balls 

 entered were either partially or completely cicatrized in cases of 

 wound of the socket; which led him to suppose that, as the tusk 

 is an organ of double growth, the membrane of the follicle and 

 the pulp both play important parts in the process of enclosure, 

 and that there is no reg-eneration of true ivory, — an hypothesis 

 which was afterwards verified by observation. From a conside- 

 ration of the opinions of Camper, Blumenbach, Lawrence, and 

 Cuvier, it appeared that doubts are entertained as to the existence 

 of cicatrices after wounds of the tusk, and opinions held as to the 

 impossibility of the occurrence of such phenomena in a non-vas- 

 cular substance like ivory. To investigate this subject with suc- 

 cess, two principles must be kept in view : first, that a tusk is 

 formed from within outwards, as well as from without inwards; 

 and secondly, that the ivory and cement are never changed by 

 vital action in form or substance, after their original deposition." 

 With these two principles, the author proceeded to explain the 

 healing of different wounds of the tusk, and the mode of enclosure 

 of balls and other foreign bodies, by describing in detail the de- 



