Cold has, from the time of Hippocrates, been regarded as a great predisposing if not exciting cause, and the non-traumatic cases have been classed together as those a frigore. It is not, however, the exposure to simply a low temperature that is followed by the disease, but to cold combined with dampness, and quickly succeeding to a temperature decidedly higher, as in the cool nights coming on after hot days in tropical regions, or in the spring and fall seasons of temperate latitudes, or in the cold air blowing over or cold water dashed upon a wound or the heated skin. That such cold, thus operating, does most usually precede the attack of tetanus is unquestionable; and it has by many been held that without it no traumatism will be followed by the disease. Observers generally are agreed, with Sir Thomas Watson, that “there is good reason for thinking that in many instances one of these causes (wound and cold) alone would fail to produce it, while both together call it forth.”
In the low lands of hot countries (as the East and West Indies) the disease is very frequently met with, at times prevailing almost epidemically; and, on the other hand, it is rare in dry elevated regions and in high northern latitudes, as in Russia, where during a long military and civil experience Pirogoff met with but eight cases. Trismus nascentium would seem to be an exception to the general rule of the non-prevalence of tetanus in places far north, since, e.g., it has been at different periods very common in the Hebrides and the small islands off the southern coast of Iceland. But these localities, from their peculiar position, are not extremely cold, and their climate is damp and variable; so that, even if the lockjaw of infants be accepted as a variety of true tetanus, the geographical exception indicated is but an apparent one.
Traumatic cases are greatly more numerous than idiopathic, and no class of wounds is free from the possibility of the supervention of tetanus. Incised wounds are much less likely to be thus complicated than either of the other varieties, though operation-wounds of all sorts, minor and major, have been followed by this affection. So frequently has it been associated with comparatively trivial injuries that it has become a common belief that the slighter the traumatism the greater the danger of tetanus. That this is not true the records of military surgery abundantly show. Wounds of the lower extremity are much graver in this respect than those of the upper. Injuries of the hand and feet, especially roughly punctured wounds of the palmar and plantar fasciæ (as, e.g., those made by rusty nails), have long been regarded as peculiarly liable to develop the disease, and accidents of this nature always give rise to the fear of lockjaw. Though there can be no question but that more than one-half of the cases of tetanus in civil life are associated with wounds of these localities, yet the number of such injuries is so much greater than of those of other parts of the body that the special liability of the subjects of them to become tetanic may well be questioned. In this connection it is a significant fact that during our late war of perhaps 12,000 or 13,000 wounds of the hand, only 37 were followed by tetanus, and of 16,000 of the foot, but 57. A few years ago numerous cases of tetanus were observed in our larger cities complicating hand-wounds produced by the toy pistol—injuries that were often associated with considerable laceration of the soft parts, and generally with lodgment of the wad.
Not even the complete cicatrization of a wound altogether protects against the occurrence of the disease, the exciting cause of which, under such circumstances, is probably to be found in retained foreign bodies or pent-up fluids.
ETIOLOGY.—Almost universally regarded as an affection of the central nervous system, inducing a heightened state of the reflex irritability, though some have maintained that the reflex excitability of the medulla and the cord is actually lessened, how such affection is produced is unknown; and it is an unsettled question whether it is through the medium of the nerves or the vessels, whether by ascending inflammation, by reflected irritation, or by the presence of a septic element or a special micro-organism in the blood.
That the disease is due to ascending neuritis finds support in the congested and inflamed state of the nerves leading up from the place of injury (affecting them in whole or in part, it may be in but a few of their fibres), and in the inflammatory changes discoverable in the cord and its vessels. But time and again thorough and careful investigation by experienced observers has altogether failed to detect any alterations in the nerves or pathological changes in the cord, other than those that might properly be attributed to the spasms, the temperature, or the drugs administered. The symptoms of acute neuritis and myelitis (pain, paralyses, and later trophic changes) are not those which are present in cases of tetanus. The evidences of inflammation of the cord are most apparent, not in that portion of it into which the nerves from the wounded part enter, but, as shown by Michaud, so far as the cellular changes in the gray matter are concerned, always in the lumbar region, no matter where the wound may be located.
The much more generally accepted theory of reflex neurosis is based upon the association of the disease with “all forms of nerve-irritation, mechanical, thermal, chemical, and pathological;” upon the direct relation existing between the likelihood of its occurrence and the degree of sensibility of the wounded nerve;2 in the, at times, very short interval between the receipt of the injury and the commencement of the tetanic symptoms; in the local spasms unquestionably developed by nerve-pressure and injury; in the primary affection of muscles at a distance from the damaged part; in the already-referred-to absence of the structural lesions of inflammation; and in the relief at times afforded by the removal of irritating foreign bodies, the temporary cutting off of the nerve-connection with the central organs, or the amputation of the injured limb. But that something more than irritation of peripheral nerves is necessary to the production of tetanus would seem to be proved by the frequency of such irritation and the rarity of the disease; by the not infrequent prolonged yet harmless lodgment of foreign bodies, even sharp and angular ones, against or in nerves of high sensibility;3 by the primary affection of the muscles about the jaws, and not those in the neighborhood of the wound; by the almost universal failure to produce the affection experimentally, either by mechanical injuries or by electrical excitations; by certain well-attested instances of its repeated outbreak in connection with a definite locality, a single ship of a squadron, a particular ward in a hospital, or even bed in a ward; by the usual absence of that pain which is the ordinary effect of nerve-irritation; and by the small measure of success which has attended operations, even when early performed, permitting the taking away of foreign bodies pressing upon or resting in a nerve, interrupting the connection with the cord, or altogether removing the wound and its surroundings. Even in the idiopathic cases—many of which, it would at first sight appear, can be due only to reflected irritation—another explanation of the mode of their production may, as we will see, be offered.
2 According to Gubler, the danger is greatest in wounds of parts containing numerous Pacinian corpuscles.
3 Heller has reported a case in which a piece of lead was lodged in the sheath of the sciatic nerve. Though chronic neuritis resulted, the wound healed perfectly. Two years later, after exposure while drilling, the man was seized with tetanus and died of it.
The so-called humoral theory would find the exciting cause of the disease in a special morbific agent developed in the secretions of the unbroken skin or the damaged tissues of the wound, or introduced from without and carried by the blood-stream to the medulla and the cord, there to produce such cell-changes as give rise to the tetanic movements. It finds support in the unsatisfactory character of the neural theories; in the strong analogy in many respects of the symptoms of the disease to the increased irritability and muscular contractions of hydrophobia and strychnia-poisoning, or those produced by experimental injections of certain vegetable alkaloids; in the recent discoveries in physiological fluids, as urine and saliva, of chemical compounds,4 and in decomposing organic matter of ptomaïnes capable of tetanizing animals when injected into them; in the rapidly-enlarging number of diseases known to be, or with good reason believed to be, consequent upon the presence of peculiar microbes; in the more easy explanation by it than upon other theories of the ordinary irregularity and infrequency of its occurrence, its occasional restriction within narrow limits, and its almost endemic prevalence in certain buildings and even beds; in the extreme gravity of acute cases and the protracted convalescence of those who recover from the subacute and chronic forms; in the very frequent failure of all varieties of operative treatment; and in the success of therapeutic measures just in proportion to their power to quiet and sustain the patient during the period of apparent elimination of a poison or development and death of an organism.