(9) Whether proteolytic ferments, and even resembling the autolytic, arc present in the milk, as is a priori not improbable; or whether the effects attributed to these are clue to bacteria alone, is no better determined than is the presence of rennin ferments.
(10) On the other hand, their coagulative effect on hydrocele fluid is certain.
Colostrum and centrifugal sediment, because of their abundant cellular constituents, contain more superoxidases and probably also more reductases and alciehydases than does normal milk. Colostrum contains peroxides even when normal milk contains none, or only traces. A more abundant appearance of the ferments known collec tively as oxidases goes band in hand with the presence of colostrum constituents in normal milk—for example. in that of women. A quan tative determination of the peroxidases in human milk can in this sense take the place of a microscopical examination. Moreover, most of the clata concerning the quantitative relations of the ferments in the different kinds of milk are unreliable or worthless, for the effect of the ferments depends on the reaction, the quantity of salt, and many other circum stances. The number of bacteria in the milk is also an important factor.
The alexins of the milk are derived in part from the transuded serum, and in part from the glandular cells. All the alexins produced in the body of the animal, either by experiment or by disease, pass into the milk. Between the amount in the milk and that in the blood serum there exists, in some cases, an invariable ratio (1:200 diphtheria anti toxin in horses). On the other hand, milk, and especially colostrum, is richer in agglutinins than is blood serum. Cow's milk has normally a marked germicidal potency against the cholera vibrio and checks the growth of the dysentery bacillus. Its effects upon the bacteria of typhoid, paratyphoid, enteritis, and diphtheria, and upon colon and milk sapro phytes are, however, insignificant. Human milk is believed to check the growth of typhoid bacilli in a. slight degree. On the other hand, the milk of women in the first weeks after parturition, colostrum especially, abounds in agglutinins for the blood of both men and rabbits. The htcmo lysis due to staphylolysins, vibriolysins, agaricin, saponin, etc., is checked
by the milk (woman's, cow's, goat's). The agglutinating agent appears to reside in the serum of the milk. Finally, the action of human milk in preventing the coagulation of cow's milk has been attributed to its property of neutralizing rennin. Goat's milk does not possess it. The absorption of the alexins of milk from the alimentary canal appears to occur only in the case of young animals and only when united with the proteids from the same species, and even under such conditions does not always follow (e.g.. tetanus antitoxin in the horse, typhoid aggluti natus in rabbits, guinea-pigs, and cats). The influence of the digestive ferments is here important.
Milk contains, inorganically combined, K, Na, Ca, Mg, Fe, 0, N, P.O.,, CI, CO_ traces of Al, Si, Mn, Fl, I, and perhaps also Milk ash contains carbonates, phosphates, and sulphates, and perhaps even iron which has arisen from organic compounds by incineration. Not all the salts, even leaving out of the question the bases united with the casein, are found in perfect solution. On the contrary, a part of these, particularly Ca and are precipitated by mechanical action; e.g., by long standing, by filtration through porcelain filters, and by centrifugation. The gases, particularly are given off by simple standing.
Between 0.2 and 0.4 per cent. of unknown substances may be present in the milk. This, however, is assumed on arithmetical rather than chemical grounds and appears doubtful. These "residues" become nu merous only in colostrum, of whose proteids (see Laelomuein, above) we have no adequate knowledge.
The color of milk is caused by the reflection of light from the sus petaled particles of casein and from the fat globules. Skimmed mill; looks blue because the blue rays are more strongly reflected.
The specific. gravity is lowered by a high content of fat and raised by one of salts. A milk poor in fats can thus be brought to the normal specific gravity by watering it. During several hours after milking, or after being warmed, the specific gravity rises as much as 0.0015. This is due to the contraction of the stiffening milk globules.