MEMOIR OF BARON HALLER. 3>RNlA 



bilityistoosoft. Some polypi, though very soft, are 

 BO irritable as to he affected even hy the light. 

 Irritability then, is a property of animal fibre, in 

 the same way as attraction and gravity are properties 

 of matter in general ; and all that can be done is 

 to explain the phenomena presented by this quality 

 of fibre, without entering into useless speculative 

 inquiries. 



We may add, that to Haller we apparently owe 

 the discovery that the iris is not muscular. His 

 words are, " You will be surprised to learn that the 

 iris has no irritability, when the cause of irritation 

 applied is mechanical. I have observed that its 

 dilatation does not depend upon muscular force. 

 After death it still remains dilated; and the phe- 

 nomena presented in animals, whether cold-blooded 

 or hot, harmonize with this view." 



Such, then, is a very short analysis of one of 

 Haller's treatises on this important subject; and 

 instead of here expressing any opinion of our own 

 concerning it, we shall subjoin a few sentences 

 which embody the opinion of the celebrated Tissot, 

 who took an early opportunity of introducing it to 

 the notice of his countrymen in a French translation. 

 " The great discovery of the present day is irritability, 

 described in the accompanying treatise ; in praise of 

 which I shall say nothing, seeing its celebrated 

 author, for these twenty years past, has favoured 

 the public with so many excellent performances, 

 and now this subject is become the principal topic 

 of all those who devote themselves to the important 



