14 



Dr. A. Dowries. On the 



[Jan. 14. 



About this region there is a system of arched commissural fibres, 

 the librae arcuatse. They seem to be connected with the crura cere- 

 belli and medullam. They occur not only through tbe external part 

 of the ventral surface, but also through the central portions. 



The acusticus and glossopharyngeal arise from the grey substance 

 on the floor of the fourth ventricle. 



The vagus arises from a series of rounded tuberosities situated on 

 the side of the floor of the fourth ventricle ; each root arises from a 

 separate tuberosity. 



The spinal nerves arise by dorsal and ventral roots ; the latter from 

 the ventral horn of grey substance. The former pass obliquely into 

 the interior of the cord and there divide into two bundles ; one bundle 

 from the anterior part of the root is directed backward, the other 

 bundle from the posterior part of the root is directed forward. They 

 pass over the next nerve both in front and behind, and join the 

 lateral columns of the cord. This arrangement was first described by 

 Stieda* 



January 14, 1886. 



Professor STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " On the Action of Sunlight on Micro-organisms, &c, with 

 a Demonstration of the Influence of Diffused Light." By 

 Arthur Downes, M.D. Communicated by Professor 

 Marshall, F.R.S. Received December 9, 1885. 



Eight years ago, conjointly with my friend Mr. Blunt, I commu- 

 nicated to the Royal Society an account of an experimental inquiry 

 into the action of sunlight on the micro-organisms of putrefaction 

 and decay."]* 



We adduced evidence, conclusive in our opinion, that the solar 

 rays were very hostile to these lowly forms of life ; so much so that 

 under favourable conditions bright sunlight, sufficiently prolonged, 

 would altogether prevent their appearance in fluids which, under 



* " Zeitsch. f. Wiss. Zoologie," Bd. 23, 1873. 



f " Proc. Roy. Soc," vol. 26, p. 488, and vol. 28, p. 199. 



