270 Drs. Fagge and Stevenson on Physiological Tests [May 18, 



Received May 18th, 1865. 



Since the above note was sent in to the Society, I have completed the de- 

 monstration for the 7th degree, and in the course of the inquiry have had 

 occasion to consider the conditions to be satisfied in order that a rational 

 function of x, with r equal roots a, may undergo no loss of real roots for 

 any assigned variation imparted to the function : for the theory of the 7th 

 degree the case of three equal roots has to be considered, and the conditions 

 in question are that the variation itself may contain the equal root a, and 

 that its first differential coefficient may have the contrary sign to that of 

 the third differential coefficient of the function which it varies when a is 

 substituted for x a theorem which is, of course, capable of extension to 

 the case of an equation passing through a phase of any number of equal 

 roots*. 



II. " On the Application of Physiological Tests for certain Organic 

 Poisons, and especially Digitaline." By C. HILTON FAGGE, M.D., 

 and THOMAS STEVENSON, M.D. Communicated by J. HILTON, 

 F.R.S. Received May 4, 1865. 



(Abstract.) 



As the chemical processes for the detection of certain organic poisons 

 are very inconclusive in their nature, and as many of these agents produce 

 effects of a most remarkable kind on the lower animals, it is not surprising 

 that their physiological action should have been employed as a test for 

 their presence. Thus Dr. Marshall Hall suggested as a means of discover- 

 ing strychnia, the tetanic symptoms which that alkaloid causes in frogs ; 

 and quite recently MM. Tardieu and Roussin produced a large mass of 

 physiological evidence, in a French "cause celebre", in which digitaline 

 was believed to be the poison used. 



Those who have recommended the employment of evidence of this na- 

 ture have always relied on the similarity between the symptoms observed 

 in the case of supposed poisoning during life, and the effects obtained on 

 the lower animals by the extract believed to contain the toxic agent ; and 

 as the action of poisons on man and on the lower vertebrata is certainly 

 not always the same, the value of these physiological tests has been much 

 disputed, and is not now admitted by most authorities in this country. It 

 appears to us, however, that physiological evidence may be made inde- 

 pendent of any relation of this kind. It is sufficient that the action of the 



* The above is on the supposition that one of the three equal roots remains unaffected 

 in magnitude by the variation, whilst the other two' change. If all three are to change 

 simultaneously, infinitesimals beyond the first order and with fractional indices have to 

 be brought into consideration; in that case, on making x=a, the variation need not 

 become absolutely zero, but must contain no infinitesimal of the first order. And a 

 further limitation becomes necessary in addition to the conditions stated in the text, in 

 order that no loss of real roots may be incurred in consequence of the variation. 



