STIMULI AND THEIR ACTIONS 



359 



extremities by contracting their muscles, and stands, sometimes 

 more than an hour, in this grotesque position (Fig. 152, B). By 

 the proper operations it can be determined that by the mechanical 

 stimulation of the skin the ganglion-cells at the base of the mid- 



Fio. I'yl. — Fl-og that haslieeu deiirived of liis cerebrum. A, In tlie customary squatting attitude. 

 Ji, In tlie attitude of general rctlcxtone: the muscles of the limlis and the back are in 

 constant eontractii-ai, so that the frog stands immobile npon his raised legs in the attitude of 

 a frightened cat. 



brain are put into a tonic state of c.Kcitatidii, which is communicated 

 to all the body-muscles that arc innervated from that point. ^ 



The after-effects of many chemical stimuli, especially the 

 bacterial poisons, are the most interesting and of most practical 

 importance. It is an old experience that after recovery from certain 

 infectious diseases, such as small-pox, scarlet fever, and measles, 

 the bodies of men ami animals are immune to further infection 

 from the same' source. It is well kuiiwn that the modern thera- 



' cy. Verwoin (913, o). 



