track of the strangers. So much annual loss has resulted to the indigenous cattle of Missouri, Illinois, and other States from the transit of the Spanish herds, that an attempt was made at a great Convention at Chicago a year ago to lay down limits for the "track” of Texan cattle, so that the stock belonging to homesteads on the route should not come in the way of the foreign breed. The need for some such vigorous and concerted action has arisen out of the following circumstances:

Home-bred animals (say of Missouri) grazing on pastures over which Spanish cattle have passed and have left their excrements, are apt to be seized after an interval with symptoms of a typhus kind, that is to say listlessness, no appetite, restlessness, loss of strength, the head lowered, the back arched, the ears drooping, the horns hot, the eyes dull and fixed, the flanks trembling, the fæces voided at frequent intervals along with bloody mucus, the urine bloody, the breathing quick, and death ensuing in a state of stupor or convulsions. Ninety per cent. die after three or four days, or it may be after one or two days' illness. On opening the animal, sloughs, erosions, and deep excavated ulcerations are found towards the pyloric end of the rennet or fourth stomach. The disease is never communicated from one victim to another. It is caught only by grazing or otherwise following in the track of the Spanish cattle.*

Report on Texas Fever,' Parliamentary Paper, 1880 (compilation by Professor Brown, from U.S. sources).

Now, it was clear from the first that the droves from Texas did not suffer from that disease. Occasional animals among them died, no doubt, at the same time as the home-bred cattle were dying; but no amount of careful search could prove that they ever died of that fever. What they died of was something like the following: "The animal was quite emaciated, breathed hard and was evidently near death. It was killed and most critically examined throughout, without presenting appearances of any disease at all analogous to that afflicting the native cattle; in fact, there seemed to be no disease, but a wasting away of the animal, and a dying of poverty. The fatty tissues had all been absorbed in sustaining life, and the system did not seem to have vitality enough to rally from the fatigues the animal had undergone on the journey."* Indeed, illness of any definite kind besides lameness was rare among the Spanish cattle; they rapidly improved in condition after a few days' grazing, although it was admitted that sometimes a considerable percentage of the herd had dropped by the way. A Commission sent out from Chicago in 1868 came to a locality where the home-bred cattle had become infected, and they set to work to find traces of disease among the Spanish cattle: "We travelled over twenty miles back on the trail, never out of sight of these cattle, which were estimated to number from 25,000 to 30,000 head. Much time was spent in riding through and examining the cattle, and quite a number * L. c., p. 16.

were caught with the lasso and their temperature and pulse taken and their feet examined. Two days were thus spent without finding any animal that could be called sick" (p. 18). There is in fact complete practical agreement among all sensible people along the "track" that the Spanish cattle do not suffer from Texas fever, although that fever is caught from them by the home-bred cattle, and is never caught in any other way.

The factors in the production of this remarkable vicarious infection are twofold: first, the hardships of the journey; and, second, the wide differences in breed. It is not likely that the infection would be so uniform in its incidence but for the existence of both of those factors. Its conformity of type is due to the steady operation of the same two factors, season after season; the infecting animals have been always of a widely different race, and they have undergone a trying journey from a totally different sort of climate and country.

It is noteworthy that Texas cattle "removed to localities characterised by the same climatic conditions (as from one portion of the Gulf Coast to another, or upon the same parallel of latitude) do not communicate disease to local stock;" and again, that "in portions of Arkansas in which the climatic conditions are similar to those of the region from which the migrating cattle come, no infection occurs." There are many other subsidiary facts of a like kind, upon which I cannot enter; but there are no facts conflicting with

the doctrine that the fever is a vicarious infection, a short and sharp illness caught from animals of a widely different breed, after they had come thousands of miles by road, rail, and river-boat, and had become inured to the well-known hardships of that kind of cattle-transit. I do not say that Texas fever is the infective equivalent of the hardships alone; it is the infective equivalent of hardships borne by cattle of a widely different breed. The infection is contingent, as infection so often is; but the home-bred cattle are so uniformly different in condition, acclimatisation and racial characters, that the contingency is almost a certainty.

Whether mere contact alone, amidst these racial and climatic differences, would induce a fever is a curious question, but hardly a practical one; for the reason that the new arrivals will always bear the effects of a journey or voyage in one degree or another. Thus, in the instances from the South Seas, or in the well-known case of strangers arriving at St. Kilda, there is always the fact of confinement on board ship; or, as Darwin says, the set of men whose effluvium would appear to be poisonous when inhaled by others ("and possibly more so if the men be of different races") had been "shut up some time together."*

I have endeavoured on various occasions to recommend this doctrine of vicarious infection as suitable to those mysterious and annoying outbreaks of foot* Naturalist's Voyage round the World,' p. 436.

and-mouth disease which now and then appear in the midst of the country, when every way of ingress is closed. New purchases, especially of Irish stock which had been driven for weeks from market to market, may give foot-and-mouth disease to homebred stock with which they come into contact, although they do not themselves suffer from the acute specific malady. The practical bearing of such a doctrine is that all new purchases should be carefully keep apart from the home-bred stock, until such time as the former are acclimatised or the newness of their position worn off. Where breeds of cattle are broadly distinguished, or racial characters strictly cultivated, such precautions are all the more necessary, and most of all necessary where the strangers are just off a journey. This will prove a better working rule than the threadbare dogmatism about there always being pre-existing cases somewhere, preferably in a foreign country.*

The great instance of a vicarious infection in human pathology is yellow fever. It would take too long to go into the complex facts fully, and I must content myself with a brief summary of views that I have developed at length elsewhere.†

The element of racial difference in this case of vicarious infection is supplied by the wide gulf which separates the white man from the African negro, who, 'for his part, can hardly take yellow fever although he *See Fortnightly Review,' Aug., 1883; and Field,' May 24th, 1884.

+ See 'North American Review,' Oct., 1884; and 'Brit. Med. Journ.,' August 4th, 1883.