Many of these observations made with the albumoses I have repeated with several of the proteoses and peptones more recently studied, as protocaseose, protoelastose, the globuloses, and others. The results may be taken as practically confirmatory of the older observations, and I make mention of them in this general way simply to emphasize the fact that all of the proteoses, though perhaps showing individual peculiarities, are possessed of marked physiological properties, which plainly testify to their toxic nature, when introduced directly into the blood-current.
Young animals are particularly sensitive to the injection of proteoses into the blood, even when the introduction takes place very gradually.[154] Thus, a young, healthy dog of 2 kilos. body-weight, eight weeks old, died in one hour after the injection into the jugular vein of 1 gramme of protoalbumose in 20 c.c. of water, thus affording a good illustration of the extreme toxicity of this albumose when introduced directly into the blood.
Of greater interest, physiologically, are the changes the individual proteoses undergo after their injection into the blood. As already stated, peptone so injected may appear in the urine wholly unaltered. Thus, Neumeister[155] has made injections of both amphopeptone and antipeptone in the case of dogs, and was able to detect the peptone very quickly in the urine. I have made like experiments with other forms of peptone and obtained similar results; thus, a pure amphopeptone formed from casein by pepsin-proteolysis (2 grammes in 15 c.c. water) was injected into the jugular vein of a dog weighing 5 kilos. The urine collected during several hours after the injection was heated to boiling, and saturated while hot with ammonium sulphate. The filtrate, on being tested with cupric sulphate and potassium hydroxide, gave a fairly strong biuret reaction for peptone. Another similar experiment made with antipeptone, formed from the myosin of muscle-tissue, gave like results.
With proteoses, however, different results are obtained, as Neumeister[156] first pointed out. These bodies introduced into the blood undergo more or less of a change prior to their excretion in the urine, the change partaking of the character of a hydrolytic cleavage in which the primary proteoses are transformed into secondary proteoses, while deuteroproteoses are changed into peptones. This is not necessarily to be interpreted as meaning that the full equivalent of the proteose injected appears in the urine, but that the portion which is eliminated through the kidneys tends to undergo a transformation somewhere en route, akin to the change produced in pepsin-proteolysis. As to how common or complete this transformation is under the above circumstances, we have no positive knowledge. Such a hydrolytic change certainly occurs in the case of the dog, and the experimental evidence is in favor of the view that the transformation is effected in the kidneys by the pepsin secreted through the urinary tubules, where there is momentarily a formation of free acid. In the rabbit, on the other hand, no such change occurs; the urine from this animal contains practically no pepsin, and consequently the proteoses eliminated through the kidneys are excreted unaltered. As, however, the experiments of Stadelmann[157] and others have shown that the urine of all carnivora, and of man as well, contains a ferment which, on the addition of a suitable amount of hydrochloric acid, will digest fibrin with formation of the ordinary products of pepsin-proteolysis, it is to be presumed that all proteoses passing through the kidneys will undergo at least some change prior to their excretion in the urine.
However this may be, it is very evident that the proteoses formed in gastric digestion cannot be absorbed as such directly into the blood-current. Introduced into the blood, they behave in such a manner as to warrant the conclusion that they are truly foreign substances, and the system makes a brave endeavor to remove them as speedily as possible. The same may be said of amphopeptones, from which we may conclude that all of these products of pepsin-proteolysis undergo some transformation during the process of absorption, by which their toxicity is destroyed and their nutritive qualities rendered fully available for the needs of the body. Discussion of this question, however, will be left until the next lecture.
In view of these pronounced physiological properties of the proteoses, it is interesting to recall the now well-known fact that many of the chemical poisons produced by bacteria are proteose-like bodies, chemically, at least, closely akin to the proteoses resulting from pepsin-proteolysis. Thus, Wooldridge[158] as early as 1888 pointed out that an alkaline solution of tissue-fibrinogen exposed to the action of anthrax-bacilli suffered some change, so that when introduced into the blood it possessed the power of producing immunity to anthrax. This observation was verified by Hankin,[159] who further showed that the substance formed by the anthrax-bacilli was a veritable albumose, and that it truly possessed the power of producing immunity. Sidney Martin[160] carried the matter still further, and by growing the anthrax-bacilli in a pure solution of alkali-albuminate prepared from blood-serum, proved the formation of both primary and secondary albumoses, as well as of peptone, leucin, tyrosin, and a peculiar alkaloidal substance of pronounced toxic properties. Martin finds that the albumoses are not as poisonous as the alkaloid, and surmises that the alkaloid is contained in the albumose molecule in the nascent state; further, he suggests that the albumoses in small doses may exert some protective influence, while in larger doses they act as vigorous poisons. How true this may be I cannot say, but my own experience convinces me that the anthrax-bacilli grown in a culture medium composed of alkali-albuminate, prepared from egg-albumin, to which the necessary inorganic salts and some glycerin have been added, do give rise to albumoses and peptones which are truly endowed with toxic properties.
Albumose-like bodies have also been obtained by Brieger and Fränkel[161] with the bacillus of diphtheria. These, too, were endowed with powerful poisonous properties, and when introduced into the tissues of the body gave rise to reactions resembling those produced by the Löffler bacillus. In my own laboratory, recent experiments made with the bacillus of glanders have shown that when grown in a slightly acid medium containing alkali-albuminate, albumoses, peptones, and crystalline bodies such as leucin and tyrosin are formed in considerable quantities. Kresling[162] has reported similar results. With the tubercle-bacilli, many like results have been recorded. Thus, among others, Crookshank and Herroun[163] have reported the finding of albumoses, peptone, and a ptomaine when the bacilli have been grown in glycerin agar-agar, and also in fluid media.
Koch[164] has made a special study of the albumose which he considers as the specific toxic agent of the so-called tuberculin. This albumose was found by Brieger and Proskauer[165] to have a somewhat peculiar composition, inasmuch as it contains forty-seven to forty-eight per cent. of carbon and only 14.73 per cent. of nitrogen, agreeing, however, in this respect very closely with the peptone formed from egg-albumin by the action of bromelin.[166] Still more recently, Kühne[167] has made a thorough study of this albumose, as well as of the other products elaborated by the growth of the tubercle-bacillus. He designates all of the peculiar albumoses formed by these bacilli as acrooalbumoses. They are endowed with marked chemical and physiological properties, causing a rise of temperature when injected into the blood, as well as other phenomena more or less pronounced. It is thus evident there is ample ground for the statement that all nutritive media in which pathogenic bacteria have been planted are liable to contain, sooner or later, toxic substances, many of which at least are closely related to, if not identical with, the albumoses. It is not my purpose, however, to consider these points in detail, nor to quote the many results obtained by other workers in this direction.
I wish merely to call attention to the fact that the proteoses, and likewise the peptones formed by pepsin-proteolysis, are more or less toxic when introduced directly into the blood, and that they share this property with the proteoses formed by bacterial organisms, or by the enzymes which they give rise to. In other words, these primary cleavage or alteration products of the proteid molecule, however produced, are more or less poisonous, and if introduced into the blood-current without undergoing previous change may show marked physiological action. It is, of course, not to be understood that these bodies are all alike. They are surely closely related and possess many points in common, especially so far as their chemical properties are concerned, but their chemical constitution and their physiological action must vary more or less with their mode of origin.