1877.] On the Automatic Action of the Sphincter Ani. 77 



perature, and adopting that o£ the f using-point of the metal as determined 

 by Balfour Stewart, we get 



From A 14-1948 at -38°-85 C. 



„ B 14-1920 „ „ 



„ C 14-1929 „ 



and, as a final mean of these three, 14-1932 as the number representing the 

 density of solid mercury at its fusing-point as referred toivater at 4° C. taken 

 as unity. I think this result (which, it will be seen, differs considerably 

 from the figures hitherto quoted) may be fairly accepted with confidence. 



In these experiments most of the weighings were made by Adjunct 

 Professor Dunnington, and the freezing-mixtures were managed, at no 

 small cost of personal discomfort, by Messrs. Bryan and Memminger, 

 students in this Laboratory. To these gentlemen my thanks are due. 



IV. "The Automatic Action of the Sphincter Ani/' By W. 

 R. (towers, M.D., Assistant Physician to University College 

 Hospital. Communicated by J. S. Burdon Sanderson, 

 M.D.j F.R.S., Jodrell Professor of Human Physiology in 

 University College, London. Received February 24, 1877. 



The observations described in the following paper had for their object 

 the determination of the form of the reflex or automatic action of the 

 sphincter ani of man when voluntary power over it is lost. This reflex 

 action is believed, from the researches of Masius*, to depend on an 

 " ano-spinal centre," situated in the lumbar enlargement of the spinal 

 cord, controlled in health by higher (encephalic) centres. It appears, 

 however, to be very uniform in its character in various conditions, the 

 most conspicuous common character of which is the entire loss of 

 voluntary power. 



The larger number of observations were made on a man who, by a 

 violent fall on the sacrum, had apparently injured the posterior roots of 

 all the sacral nerves and both roots of the lowest sacral nerves. A de- 

 pression existed over the lower part of the sacrum. Sensibility to touch 

 and pain was lost in all parts supplied by branches from the sacral 

 plexus, the Hmitation being exact. There was no muscular paralysis or 

 loss of nutrition except in the levator ani, the sphincter ani, and the 

 sphincter vesicae, all of which were paralyzed to the will. The anus and 

 the mucous membrane of the rectum were quite insensitive. There was 

 no evidence of any injury to the spinal cord ; with this, indeed, the 

 symptoms were incompatible. It would thus appear that the only 

 lesion was a division of the direct communication between the sphincter 



* Bull, de l'Academie Royale de Belgique, 1867. t. xxiv. p. 312, and Journal de 

 l'Anatomie et Physiologie, 1868, p. 197. 



