326 LECTURE XIV. 



produces an effect upon the magnetic needle now we 

 are able, by means of this physical experiment, with 

 certainty to judge when a nerve is dead, for, as soon as 

 death has stepped in, those qualities cease, which are in- 

 separably connected with the life of the nerve. 



This peculiarity which we find in some parts exhibited 

 in such a marked degree and so evidently demonstrable, 

 becomes less and less apparent, the more lowly the or- 

 ganization of the part, and our criteria are least to be 

 depended upon in the case of the class of connective 

 tissues ; for we are, indeed, really frequently much puz- 

 zled to decide whether a part composed of one of them 

 is still alive or has already perished. 



If now we proceed with our analysis of what is to be 

 included in the notion of excitability, we at once dis- 

 cover, that the different actions which can be provoked 

 by the influence of any external agency, are essentially 

 of three kinds ; and I consider it of great importance 

 that you should pay particular attention to this point, as 

 it will greatly assist you in the classification of patholo- 

 gical conditions, and because it is not wont to be set forth 

 with particular distinctness. 



When, namely, a given action is called into play, we 

 have to deal with a manifestation either of the function, 

 the nutrition, or the formation of a part. It certainly 

 cannot be denied that at certain points the boundaries 

 between these different processes disappear, and that 

 between the nutritive and formative processes and also 

 between the functional and nutritive ones, there are tran- 

 sitional stages ; still, when they are typically performed, 

 there is a very marked difference between them ; and 

 the internal changes which the individual excited part 

 undergoes, according as it only performs its functions, or 

 is subjected to a special nutrition, or becomes the seat 

 of special formative processes, exhibit considerable dif- 



