404 TETANUS. 



on physiological principles ; in many respects a not unsatisfac- 

 tory manner of arriving at an understanding of the pathology 

 of tetanus, although failing to explain every phenomenon. 

 The power of reacting on motor- nerves — i.e., of generating an 

 impulse within itself, on reception of a centripetal impression, 

 which resides in the spinal dynamic matter, and which Dr. 

 Todd named polarity — is that Avhicli in this view is regarded 

 as the origin or cause of tetanic spasm. 



This power is subject to very great modifications, both as 

 respects its susceptibility of being excited by stimulants, 

 and the extent and force with Avhich it is exerted. In ordinary 

 circumstances the voluntary muscles are, as a rule, exempt 

 from its influence, but in certain diseases they are so acted 

 upon or overpowered that the will has little or no control over 

 them. 



Considering these facts, and reasoning on this principle, it is 

 thought, by those who hold this view, fairly well established 

 ' that the phenomena of the tetanic condition result from an 

 exalted polarity of the centres supplying the parts affected. 



' In cases of traumatic tetanus the exaltation of the polar 

 state commences in the afferent nerves of the seat of the 

 wound ; if the tetanus arises from cold, the exalted polarity 

 commences in the nerves of common sensation, distributed to 

 the exposed part ; from the periphery thus irritated the con- 

 dition is propagated through the nerves to the centres, and 

 the effects on the muscular system show to what portions of 

 the nervous centres the exaltation of the polar force is com- 

 municated. 



' This, however, does not afford an adequate explanation of 

 the production of tetanus, and it is well known that it is im- 

 possible, even by severe mutilation, to j)roduce tetanus in the 

 lower animals; whereas a slight accidental injury (as when a 

 nail penetrates a horse's foot) will often excite the disease in 

 its worst form. It would seem that some particular state of 

 the system, probably some peculiar condition of the blood, is a 

 necessary precursor of this malady. Hence, no doubt, its 

 greater frequency in warm and unhealthy climates, in over- 

 crowded and badly ventilated hospitals, and among ill-housed 

 and ill-fed subjects. That tetanus may be produced through 

 the blood is shown by the results t)f the administration of 



