334 PHYSIOLOGY CHAP. 



(6) They depend on external trauma or irritation, against which 

 the operated animal is no longer able to protect itself; 



(c) They depend on both these factors, since the neuro-paralytic 

 hyperaemia makes the tissues more vulnerable to external injuries ; 



(d) They depend on loss of the influence of the nerves which 

 regulate the nutritive processes and metabolism of the tissues. 



The first hypothesis, supported by Fodera, Magendie, Longet, is 

 clearly controverted by the experimental results of Bernard, 

 Sinitzin, and Spallitta, which show that, on the contrary, under 

 special conditions, hyperaemia may even promote the nutrition of 

 the tissues. Moreover, the hypothesis takes no account of the 

 fact that hyperaemia is a transitory phenomenon and that the 

 trophic lesions often make their first appearance after it has 

 disappeared. 



The second theory, first propounded by Snellen and Bonders, 

 is based on the fact that after section of the trigeminal or of the 

 facial nerve the panophthalmitis could be warded off for six to ten 

 days if the eye were artificially protected from injury or irritation 

 by particles of dust. It was severely shaken by the experiments 

 of Meissner, who observed panophthalmitis after a partial lesion of 

 the trigeminus which had not entirely destroyed the sensibility of 

 the cornea. On the other hand, Baldi's observations show that 

 even if traumatic irritation is often a necessary factor in trophic 

 disturbance it is not sufficient of itself to cause it. It must 

 therefore be assumed that parts which are deprived of their inner- 

 vation exhibit a lower resistance or greater vulnerability, so that 

 they can be injured by slight irritants that do not affect tissues to 

 which the nerves are intact. 



In what, then, does this lessened resistance or greater vulner- 

 ability in the denervated tissues consist ? Schiff explained the 

 panophthalmitis consequent on section of the trigeminus by the 

 third of the hypotheses enumerated above, and held that the 

 lowered resistance of the eye results from the neuro-paralytic 

 hyperaemia, owing to which particles suspended in the air, 

 which do not injure the normal eye, become the cause of 

 panophthalmitis. 



This theory, too, is in direct contradiction with the experiments 

 of Sinitzin and Spallitta. After ablation of the superior cervical 

 ganglion the neuro-paralytic hyperaemia of the eye should be more 

 pronounced than that which, according to Schiff, sets in after 

 simple lesion of the trigeminus. But the trophic disturbances in 

 the eye may be altogether absent. Schiff s view is moreover 

 inadequate to explain Baldi's interesting observations on the 

 retarded growth of hair and nails, and the slow regeneration of the 

 epidermis and cicatrisation of wounds in a limb with sensory 

 paralysis. It is evident that these, as well as the atrophy of the 

 muscles and other tissues, including the skin, are the effects of loss 



