The fact that the blood of ordinary laboratory animals exerts a very marked bactericidal effect upon the Bacillus typhosus and the Spirillum cholerae asiaticae, while it exerts little or no effect upon the Staphylococcus and Streptococcus pyogenes, has hardly received the attention which it would seem to merit in view of the circumstance that these facts involve the important problem as to whether the blood exerts its bactericidal action upon pathogenic organisms generally, or only upon certain species of such micro-organisms.

By the existing law for Great Britain it is enacted that “in every room in any factory or workshop sufficient means of ventilation shall be provided, and sufficient ventilation shall be maintained.” Not very much has been hitherto ascertained, however, as to the degree of purity actually existing in the air of factories and workshops generally, or as to what standard of purity may reasonably be expected considering the difficulties met with. A Departmental Committee was recently appointed by the Home Secretary to investigate and report upon the subject. The members of the Committee were Mr E. H. Osborn, Engineering Adviser to the Chief Inspector of Factories, and myself, with Mr C. R. Pendock, one of H. M. Inspectors of Factories, as Secretary. The Committee has just reported on the subject of general ventilation1, but reserving for a future Report the vitiation of air by dust, fumes, &c. from special manufacturing processes.

The most important of the proteid constituents of milk is casein. From 70 to 90% of the total proteids of milk consists of this substance1. In milk, casein exists as a soluble calcium compound, which is not precipitated by boiling, but from which casein is deposited by the addition of acid or by the action of rennet2. This phenomenon is known as the curdling of milk and is a preliminary to its gastric digestion, both the acid in the stomach and the rennet being capable of producing it. By artificially influencing the nature of its curd we can influence the digestibility of the milk. In human gastric digestion and in the experiments detailed below both acid and rennet are present. The curdling of milk is a necessary preliminary to its digestion in an acid medium, and by influencing this process we can also influence the digestibility of the milk.

Two questions. In concluding our review of this division of the subject, which deals with the parts played by the bodily presence of cellular protoplasm as contrasted with the activity of the chemical products of that protoplasm, which from their solubility may act at a distance from the cell producing them, there are two points which may be alluded to. Firstly, it is difficult to see how, granted that two substances are necessary for bactericidal action, these substances can in the first instance at least meet the bacterium except within a cell. Unless all immune bodies are represented in the serum by go-betweens (Zwischenkörper),—by bodies of an identical nature and differing only in that they are subservient to the normal metabolism of the body—how, when a bacterium gains entrance to the blood, does it come in contact with the immune body for which its protoplasm has the affinity? The receptor, which fixes the group in the bacterium corresponding with it, is within a cell,—how can the affinities be satisfied until the bacterium gets within the cell? It is not till the cell has been robbed of the use of these receptors and they become over-regenerated that the immune body becomes free and can be found in the serum. It is possible that all immune bodies are represented by go-betweens, and that a certain amount of the latter must be kept free in the serum for ordinary metabolism, and it is also possible that when the gradient—to use a physical phrase—between the cell and the blood plasma becomes great so far as the amount of go-betweens present in the latter is concerned that the cell becomes more active and secretes more of the material which is being more rapidly taken up than is usual in ordinary metabolism. Thus while the extra-cellular destruction of bacteria is easy to understand in the later steps of immunisation there is a difficulty about the earlier stages.