198 



COMPARATIVE ELECTRO-PHYSIOLOGY 



similar in similar specimens under normal conditions. 

 Fig. 130 gives two records of two different styles of Datura 

 alba, obtained from flowers of the same plant. The death- 

 point is seen to have occurred at 60 C. In recording the 

 thermo-mechanical curve, there is found to be, normally 

 speaking, a continuous expansion up to the death- point. 

 In the case of vigorous specimens, in a good tonic condition, 



the inversion does not take place 

 till about 59-6 or 60 C. But in 

 less vigorous specimens, a certain 

 hesitation, as it were, is seen to 

 occur in the record at or near 

 55 C. With vigorous specimens, 



FIG. 129. Photographic Record 

 of Thermo-mechanical Curve 

 given by Coronal Filament 

 of Passijlora 



The first or down part of th e 

 curve shows expansion, but 

 on reaching death-point, at 

 59*6 C., there is a sudden 

 inversion, due to spasmodic 

 death-contraction. 



FIG. 130. Thermo-mechanical Curve of 

 Two Different Specimens of Style of 

 Datura alba, obtained from Flowers 

 of the same Plant 



there may be the merest indication of this hesitation ; in other 

 cases, with less favourable tonic condition, the hesitation is 

 prolonged, but the expansion finally proceeds, and the death 

 inversion takes place at the usual temperature .of about 

 60 C. When the specimen, however, is enfeebled, or has 

 been subjected to unfavourable circumstances, the point of 

 transient instability becomes fatal, and the inversion takes 

 place there. As an example of what has just been referred 

 to namely, the influence of unfavourable external circum- 



