The result of bacteriological research indicates that the material infected is probably not large compared to the total amount used, and that in suspected samples of both hair and bristles anthrax bacilli can be isolated either by inoculation of animals or by plate cultivation.

Difficulties are met with in the inoculation of animals owing to the presence of the bacillus of malignant oedema, which, unless special methods are used as shown by Duncan, will often mask the presence of the anthrax bacillus altogether.

In separation by means of agar plates the presence of bacilli very closely resembling anthrax again leads to error. Three types of these bacilli have been met with in hair and bristles; viz.: Bac. A2 or Bac. anthracoides of Bainbridge, possibly the same as Bac. subtilis, the Bac. A1, and Bac. A. The last two do not exactly correspond with any known bacilli, and so far as we know at present are of little importance, but in view of the experiments of Gilruth showing that guinea-pigs, rabbits, and sheep can resist the inoculation of large doses of virulent anthrax bacilli completely, provided these organisms are mixed with a larger quantity of some other organisms which are non-pathogenic to these animals, and that a small amount of immunity to pure anthrax is conferred, it is certain that the presence of these anthrax-like bacilli, evidently closely related to the anthrax bacillus, cannot but be of benefit; and it is possible that further experiments may show that injections of them mixed with cultures of anthrax bacilli of varied virulence may confer a higher degree of immunity than do mixtures of anthrax with other non-pathogenic bacilli, as shown by Gilruth (1904).

1. A larger dose of toxin is necessary to kill a guinea-pig of the same weight in summer than in winter.

2. The rate of growth of guinea-pigs is more rapid in the summer months.

3. The weights of guinea-pigs are least affected by lethal doses in summer.

4. For guinea-pigs of the same weight the fatal dose increases with the age.

We are still in doubt regarding the exact position of those bacilli which, morphologically and culturally, appear to be identical with the Klebs-Loeffler bacillus but which differ from it only in the absence of specific pathogenic power for laboratory animals. Most writers regard such non-virulent strains as true diphtheria bacilli which have lost their virulence and toxigenic power either temporarily or permanently. Others however are inclined to place them in a group allied to that of the genuine Klebs-Loeffler bacillus and express doubts as to whether they at any time possessed a claim to pathological significance (Graham Smith, 1904).

(1) At present no public authority possesses legal power to deal with the question of the contamination of shellfish.

(2) It is not sufficient to test shellfish exposed for sale in a market or shop. These may have been contaminated subsequent to removal from the fishery; and multiplication of the contained bacteria may have taken place. The results of such analyses may lead to unjustifiable condemnation of a laying. It is essential that a topographical examination should be made and that samples for analysis should be taken from the laying itself.

(3) In the case of natural shellfish beds there is so much variability in the conditions with regard to the susceptiblity to pollution that a fairly large number of the animals must be examined. The labour of the analyses is therefore so great that the development of some simple routine test for faecal contamination is most desirable. Since most desirable. Since most natural shellfish layings are situated within the “sewage zone”, and therefore contain B. coli, quantitative results are essential.

(4) There are considerable differences in practial routine work in regard to the methods of isolation of intestinal organisms from shellfish; and aslo with respect to the number and nature of the reactions necessary for the identification of B. coli. It is desirable that some generally recognised series of tests should be uniformly adopted by bacteriologists engaged in such work. Further, different micro-organisms, possibly of varying degrees of significance as indicators of faecal contamination, may have been confused. There is possibly some variation in cultural characters in B. coli, and investigation of this variability is desirable. Investigation of the changes in cultural reactions undergone by intestinal organisms when entering the sea, or the tissues of marine shellfish, is also very desirable.

(5) Remedial measures other than the simple closure of a contaminated laying might be suggested. It is possible to subject the shellfish to treatment which will cause them to clean themselves of contained sewage bacteria. The source of the pollution may be removed; and sterilisation of the shellfish may be practised.