419 
March 27, 1876. 
Tur PresipeNT (PROFESSOR CLERK MAXWELL) in the Chair. 
The following communications were made to the Society: 
On the relation of the Spinal Cord to the Tail im 
“Mammals. By Mr Annineson. 
After noticing the varying position of the spinal cord and its 
nerves at different ages in man, and quoting some anatomical 
works in reference to the length of the spinal cord and the 
position of its nerves in long- and short-tailed mammals respec- 
tively, the speaker proceeded to shew that some of the state- 
ments contained in the books were not quite in accord with the 
evidence of his own dissections. The facts which he wished to 
point out were (1) The constancy of a cauda equina and filum 
terminale in both long- and short-tailed mammals; (2) The 
superficial position attained by the filum terminale towards the 
end of the tail; (8) The general constancy in the absolute 
number of sacro-caudal nerves irrespective of the total number 
of sacro-caudal vertebree; (4) The direct relation between the 
number of sacro-caudal spinal nerves and the number of ossified 
neural arches. He concluded by pointing out the relation the 
above facts might bear to the development of the tail in the 
individual and in the mammalian series. | 
On Vital Force. By Mr H. F. Baxter. 
After a few preliminary observations the author proposes the 
following question, What is the nature of Vital Force? By 
vital force he means the force that is manifested during the 
growth, development, or evolution of organised bodies, both 
plants and animals. Can we associate this force with any other 
