THE INFLUENCE OF INTESTINAL BACTERIA UPON THE THYROID GLAND

latrine," a selected and probably sequestered spot to wlich an individual will constantly; return; (3) wiat imay be designsted a "casual privy," any spot whose use the call of the moment necessitates-. Accepting these experiments it is impossible to admit that hookworm infection is a general infection of the soil, one which tends to evenness of diffusion; nor can one admit that it is of such a nature that the agriculturist mnust necessarily meet wandering larvae in the course of his work. Were this so, lhowever, we could agree with those who clearly look upon the soil as one uniform whole more or less uniformly infected, and maintain that the amount of soil inrection generally, and the consequent risk to those wlho work on it, must be proportionate to the number of'ova which fall upon it-that is, to the number of ankylo. stomes lharboured by the inhabitants. On such grounds, too, one would have to agree with Darling8 that, could one reduce the number of ankylostomes to a certain level, one would reduce the larvae they breed to a point where human infeCtion would be slight, and, if one be wiliing to coucede this without proof, negligible; and that no increase in the infection rate of a community could occur without importation of a heavier infection from outside. But, on the contrary, the evidence of Augustine's experiments is that infection must be constantly, presumably preponderatingly, a " privy " infection, and that in the case of man-made latrines and " natural latrines " it is wlhat I have termed a dejectional infection'0-obtained, that is, at the time of defaecation. Only in case of his skin cowing into contact with ground whicli has been used as a casual privy will an individual acquire what I have termed a casual infection10; and that will generally be but seldom. If;,then, one conclude "and it is diffie'ult to escape doing so -tlAt recent evidence points to hookworm infection as being undeil-ordinary conditi-ons practically always a privy infection, and preponderatingly a dejectional infection, one is confronted with tljis question: Does the man-made latrine, as recomr6ended by the sanitarian, prevent infection ; or does it actively diseminate it? There will scarcely be opposition to the *stateinwt that ankylostome infestation cannot occur from a clean sewered water-closet, wlhence the infected stool is at once removed. But in tllose widely used, because widely recommended, latrines where the stools are dealt with in 8itu with a view to larval destruction, the position is unsatisfactory and disquieting. McVail1' has found that ova and larvae, identified as those of lhookworms, are constantly present in the effluent of those fine septic tanks which stand on the banks of the Hugli; Minett12 and Khalil's have found them similarly in the West Indies; Khalil14 quotes experiments to showthat these larvae can swim; Payneu has shown that even if larvae do not migrate laterally on the surface of the ground, they can mount vertically through at least 36 inches of soil. Accordingly any latrine *hich permits of direct or indirect pollution of the soil or subsoil is, under present conditions, unsafe. 5 Since, apart from sewered latrines, there are such grave reasons for suspecting all man-made latrines as disseminators of`hbkw0orm infection, it is pertinent to inquire the extent to which a man, conscientiously using his privy and harbouring but a single pair of ankylostomes, will infect that privy. The answer lietsin the work of Baermann and of Darlina, to which reference has been made above. Assuming for the sake of even numbers -that this particular pair of worms produced 2,740 fertile eggs daily, the number deposited in the latrine 'Will be a millHon a year. We are assured that nine ankylostomes, or four to-ive millioneggs a year, are-hygienically negligible. It is not unreasonable to ask of those who are maintaining-that this prodigious figure is hygienically negligible that they should either prove it or cease to urge it as a working hypothesis. There is an unfortunate disposition to take sides on thia matter, and as one who is credited with leading the opinion that all infection matteras I would suggest that it is immaterial what anyone's opinion is, except in so far as it acts as a spur to the collection of facts. What is required is fact, and pending the collection of further facts there seems ample justification for the refusal to accept as personally or hygienically negligible any infection however Blight.