WEIMAR AND JENA. 195 



cipally to living organisms, I am now mainly directing my 

 attention to anatomy. I am receiving a course of private in- 

 struction from Loder, and devote two hours a day to making 

 anatomical preparations, so that I spend daily from six to seven 

 hours upon this subject. The remainder of my leisure I 

 employ on a great physiological work on the ' Excitability of 

 the Muscles,' of which the first volume, consisting of thirty- 

 two sheets, is to appear at Easter, while the second volume is 

 already in the press. I am gratified by finding many at Jena 

 engaged in successfully prosecuting my experiments upon ex- 

 citing vital energy by chemical means, and on increasing or 

 diminishing the powers of susceptibility. The conviction is 

 spreading that these experiments may some time lay the foun- 

 dation of a practical art of healing, and that I may thus be- 

 come the originator of a new science that of vital chemistry.' 

 In the new work above alluded to, Humboldt, by the em- 

 ployment of letters after the manner of algebraic formulae, 

 expressed the various combinations produced by different me- 

 tallic conductors and the interposition of liquids. He laid 

 great stress upon this use of signs or formulae, and remarks : 1 - 

 ' It would be impossible, either by the most careful perusal of 

 my work or the attentive examination of the tables, to gain a 

 comprehensive view of so complete an array of facts. It 

 seemed to me, therefore, important to devise a method by 

 which this want might be remedied. The convenience afforded 

 in mathematics of being able to represent a variety of propo- 

 sitions by a few analytical signs, led me to try by similar means 

 to express the changes in the galvanic apparatus where the 

 substances usually fall in a chainlike arrangement.' He ac- 

 cordingly denoted all metallic and carbonaceous substances 

 possessing power to set up a phlogistic process by the letter P, 

 and homogeneous metals two bars of gold, for instance by 

 PP, heterogeneous metals, such as gold and zinc, by Pp, and 

 moist conductors by Hh (humida). The formula 



PpP 



denotes, therefore, that a heterogeneous metal or piece of 

 carbon is in combination with two homogeneous metals ; 



1 l Versuche iiber die gereizte Muskel- und Nervenfaser/ vol. i. p. 99. 



o 2 



