Preliminary experiments were carried out during 1935, on the possible application of certain chemical substances to the problem of controlling “potato-sickness.” The results were published in two papers by Hurst & Triffitt (1935, i, ii) and it was shown that calcium cyanamide and ferric oxide were deserving of further trials on a larger scale. Field experiments were devised and carried out during 1936 in various parts of the country, and the results will be communicated when these are available. In the meantime the small-scale experiments were continued and are described below.

This communication is concerned with the field trials of substances which in previous small-scale experiments had shown promise of controlling “potatò-sickness” when they were mixed with infected soil.

The investigations described in this paper are in part a continuation of those described by Carroll and McMahon in a previous paper published in 1935. The previous paper demonstrated the fact that the root excretion of potatoes growing in recently sterilized soil does not possess the power of inducing the hatching of eelworm eggs in the normal manner. It was shown that when eelworm cysts were placed in soil leaching (containing potato root excretion) obtained from pots of very recently sterilized soil growing potatoes practically no hatch of the eggs in these cysts took place until after the lapse of about thirty days. It was further indicated that this interval of time which elapses before hatching commences diminishes according as the period between time of sterilization of the soil and time of obtaining soil leaching for hatching experiment increases.

A turkey poult sent for post-mortem examination to the Veterinary Research Division, Ministry of Agriculture, Northern Ireland, was found to be suffering from a very heavy infection of a small fluke.

In Australia this disease has occurred in many oxen on sewage farms and despite the economic loss involved, the farms have been prevented from raising cattle for human consumption. It has been claimed that this policy was adopted because of the risk to man of infestation with Taenia saginata. The object of this paper is to show that this economic waste is quite unnecessary, for cattle can be readily immunized against the disease so that there is no risk of Taenia saginata infestation in man from eating beef from such cattle.

When the beef measle bladder worm is ingested by man it is believed that the head attaches itself to the mucosa of the jejunum, the caudal bladder disintegrates and segments develop in the neck region immediately behind the head at the rate of about 6–12 per day. Thus, segments immediately behind the head one day are pushed away from the proximity of the head by the formation of new segments each day. While a segment is being pushed further from the head it increases in size and alters its shape; its sex organs, both male and female, develop and perform their functions. About 80 days are required for a segment to become ripe or for a bladder worm to develop into a complete tapeworm. The ripe posterior segments are detached almost daily. These are replaced by the formation of a similar number immediately behind the head. In this way a worm once fully grown maintains approximately the same length.

Helminth parasites in small numbers infest a very large percentage of the birds of economic importance but the damage and loss for which they are responsible has never been calculated. In considering these parasites there are two schools of thought—the first considers every helminth as a possible pathological factor and cause of death. While our knowledge of avian diseases is still rather scanty this opinion is easily understood for birds often die showing lesions in the gut and the only obvious agent is the helminths present. Recently, however, opinion has swung in the opposite direction and given rise to a second school, in which there is a tendency to discount the dangers of helminthic infestation and to minimise their importance. In the Institute of Agricultural Parasitology some caution is always adopted at post-mortem examinations before diagnosing the cause of death as being definitely due to helminths for it is felt that there are many disease factors, imperfectly understood as yet, which probably have far reaching effects on their avian hosts. However, in certain cases pathological conditions have been noticed which were undoubtedly due to helminths.

1. To determine the upper limit of the abomasal worm infestation of healthy lambs was the main object of the investigation. The results show that a lamb slaughtered fat before or shortly after weaning and therefore presumably a healthy lamb, may contain up to 2,100 Haemonchus and up to 4,670 Ostertagia.

2. Infestation with Haemonchus conlortus is negligible until August.

3. Infestation with Ostertagia remains almost steady from early May until mid-September.

4. Infestation with Trichostrongylus axei occurs from May until mid-September, but is never a heavy one.

5. The evidence suggests, but does not prove, that in mid-summer there is a wide difference in the infestation of single and twin lambs.

6. The results, so far as they affect the seasonality of infestation are, strictly speaking, applicable only to the flock of the Duthie Experimental Stock Farm, but are probably true for the North-East area of Scotland.