THE INSTINCT OF FEIGNING DEATH 185 



acting with an intelligent appreciation of his predicament, but it is 

 not to be inferred that he could have reasoned out his course of action 

 did not an innate proclivity in that direction form a part of his in- 

 stinctive make-up. 



The physiological condition in what is called death-feigning is 

 quite different in different forms. In most of the lower animals it is 

 characterized by a tetanic contraction of the muscles. The attitudes 

 assumed by many forms, such as rolling into a ball, keeping the legs 

 and other appendages drawn close to the body, or in some cases holding 

 them straight and rigid, are such as can be maintained only at the cost 

 of considerable muscular effort. If a Ranatra is picked up by one of 

 its slender legs it may be held out horizontally for a considerable time 

 without causing the leg to bend. It is as if a man were seized below 

 the knee and held out straight, face upward, without causing the knee 

 to bend ; only the legs of a Ranatra are several times more slender than 

 those of the most attenuated of the human species, and the muscular 

 tension which the insect maintains must therefore be intense. 



The death feint of insects and other low forms is not entirely 

 dependent on the brain. It is due rather to a general physiological 

 state of the animal. I have found that the posterior part of the body 

 of a Ranatra can still be induced to feign death, though less perfectly, 

 when entirely removed from the head and prothorax. When it would 

 come out of the feint a few light strokes would cause it to feign again. 

 It has been found that spiders also may still feign after entire destruc- 

 tion of the brain. 



The instinct of feigning death is doubtless closely connected with 

 much of what has been called hypnotism in the lower animals. Cray- 

 fishes, frogs, lizards, certain snakes and many birds and mammals, 

 may by a very simple process be thrown into an inactive condition from 

 which they are not readily aroused by external stimuli. In ordinary 

 death feigning the animal falls into its immobile state upon slight 

 provocation; a touch, or even a jar is sometimes all that is necessary. 

 In the so-called cases of hypnosis more or less manipulation is neces- 

 sary. The exciting cause in both cases is generally some form of con- 

 tact stimulus. In the hypnotism of animals, as Verworn and others 

 have shown, there is diminished reflex irritability, and usually tonic 

 contraction of many at least of the muscles. Similar phenomena are 

 observed in the death feigning of many forms, some of the insects 

 showing a lack of responsiveness that is truly remarkable. In a water- 

 scorpion that is feigning death the legs may be cut off one by one, or 

 the body cut in two without eliciting the least reaction from the unfor- 

 tunate victim. We can only speculate at present on the condition of 

 the nervous system which makes such a result possible. 



