find it in man, has come a long way from any primary errors of nutrition.

If, however, we analyse the process of error in tissuenutrition, we shall find that it consists essentially in inadequate provision of blood and blood-vessels.* If the primary idea of tubercle is fat gone wrong, the secondary idea is inadequate blood-supply to a redundant tissue. Whatever helps its blood-supply will help it on the road to safe obsolescence. In particular, if the natural recovery proceed as far as the fibroid condition of tubercle, the reinforcement of the bloodsupply will be clear gain, with no risk of countervailing loss. The indication is not only to make more blood, but also to make more blood-vessels; and it is not inconceivable that both of these indications are fulfilled in scrofula by a drug of proved value the iodide of iron. The same dual indication is doubtless fulfilled by much of the hygienic treatment of consumption-living much in the sunshine, breathing a dry and bracing air, exercise on horseback (Sydenham's cure), and whatever else gives the patient an appetite for and the power to digest abundant strong meats and wine.

It is in counteracting what I have called the secondary idea of tubercle, namely, the insufficient supply of blood to a redundant tissue, that the empirical treatment may be represented as most rational. But there is one kind of treatment special

* See a paper by the author on the " Physiological Type of the Giantcells of Tubercles and Granulations," Journ. of Anat. and Physiol.,' Jan., 1879. (Reprinted in Appendix to 'Bovine Tuberculosis in Man.')

to tuberculosis, namely, feeding with easily assimilated fats such as cod-liver oil, which may seem to meet the primary idea of the disease, or the idea of fat-tissue gone wrong. The best theory of the benefit of codliver oil is that it "improves the faulty nutrition which originates and keeps up the disease."* But the faulty nutrition is of a special kind, probably (in the remote causation) a diathesis-error of tissue-nutrition affecting the internal fat. Again, the beneficial action of cod-liver oil is more special in tubercle than in the cachexia of tertiary syphilis, or in nonspecific wasting diseases. Is it not an artificial help to tissue-nutrition in that very direction in which the nutrition of the organism had remotely failed? If one could believe that an infective disease carried always with it to its remotest developments the idea of the primary error out of which it arose, then it would not be altogether fanciful to ascribe some such appropriate action as that to cod-liver oil in tubercle. But I would admit as soon as anyone that the assumed cause is too distant from the known effects, and that the intermediate links of the chain are too invisible (except to the eye of faith), to make it prudent to rest the known benefits of cod-liver oil at all exclusively on that pathological indication. The other or secondary hint for treatment, to improve the vascularity by every available means, comes with much more force and directness from an analysis of the morbid process.

* J. Hughes Bennett, Principles and Practice of Medicine,' 5th ed., 1868, p. 744.

CHAPTER XIII.

VICARIOUS INFECTION AS THE EQUIVALENT OF CHRONIC HARDSHIP IN OTHERS.

THE illustrations of Unconscious Memory in Disease which have occupied us after the chapter on Visceral Neuroses may have seemed to some readers to be no illustrations of the doctrine at all. Diathesis, even where it is mostly an affair of innervation, may seem to have an explanation without invoking the power of memory. Or again, whatever the antecedents of infection may be in the way of diathesis or other chronic .and recurrent ill-health, is it not overstepping the plain meaning of words to speak of infection as summing up and propagating by means of certain representative particles a long train of vicissitudes registered in the unconscious memory?

The reason for bringing infection under the doctrine of unconscious memory is its close analogy with generation, which is itself held to be connected with unconscious memory in the manner stated in the opening chapter. With every desire to keep within the legitimate use of words I fail to see that there is anything strained or fanciful in my later applications of unconscious memory; if they are less obvious than

some of the others they are not less real. I have still to touch briefly on another kind of infection as a singular illustration of unconscious memory in disease; and therein also I venture to say that the legitimate use of words has not been overstepped.

This kind of infection is vicarious infection, a term first introduced into pathology, so far as I know, by Sir Gilbert Blane. The peculiarity of it is that it proceeds from those who are not themselves suffering from a specific form of disease. They have been inured to hardships of various kinds; but, for their own bodies, those miseries have not come to the issue of an infection, and have hardly been protracted long enough to make a diathesis. On the other hand, the individuals quickly recover their ordinary health when the steady pressure of hard and unwholesome conditions is taken off. The remarkable thing is that an infection has been breeding all the while—an infection for others but not for themselves. The infection is actually a summation of certain kinds of hardship and unnatural conditions of living; but it is in those who are well, who are as far as possible removed from the same unwholesome conditions, and most of all in those who are separated by a great gulf of racial differences, that the infection unfolds itself. It is a short and sharp equivalent in the latter class for the slow grinding of misery in the former; and therefore it is called a vicarious infection. But, it will be asked, are there actually instances in real life of that rather romantic doctrine of disease?

The instances of it mostly belong to the class of fevers marked by the peculiar prostration of typhus. They include certain historical outbreaks of typhus at the trials of prisoners (in the old days before Howard), some instances of typhus on the arrival of filthy ships, the whole of yellow fever from first to last, and, in veterinary pathology, at least one great and destructive typhus-like disease of cattle, namely, Texas fever. There is so much unwillingness to believe in this kind of vicarious fever, so much prejudice in certain influential quarters against anything that does not suit the so-called "germ-theory," and so much impatience on the part of many when they are told of principles at work too impalpable for plain men to discover, that I shall make the Texas fever of cattle my chief illustration, finding therein a body of facts that are free from all ambiguity and have been candidly accepted by practical men in the United States.

The phenomena characteristic of Texas fever had been observed from time to time early in the century in connexion with the transit of cattle from distant pasture-lands to such long-settled States as Virginia. But it is only within the last twenty years that Texas fever has become an annual visitant of the Western States, along the "track" over which the cattle of Spanish breed are driven or carried in enormous herds from the pasture-lands of Texas through Arkansas and Missouri as far up as the Canadian Lakes. The fact is known in every farm homestead along that route that it is dangerous for the home-bred cattle to graze in the