Page:The American Cyclopædia (1879) Volume XI.djvu/561

 MILK 543 another instrument, invented by Sir Joseph Banks, and called the lactometer, is used in connection with the galactometer. It is a tube about in. in diameter, and 10 in. of its length graduated in tenths of an inch. When filled with milk, the tube is set aside for 12 hours for the cream to rise. The proportion of this is then read off in the number of divisions occupied by the upper stratum. The thick- ness of this stratum is very variable with different sorts of genuine milk; but its gen- eral range is from 9 to 14 of the divisions, indicating as many percentages. Dr. Hassall thinks the average of pure milk does not ex- ceed 9| of cream. Dr. Normandy rates it at 8 to 8. The proportion of cream is also determined by an instrument invented by M. Donne of Paris, called the lactoscope, the prin- ciple of which is based upon the opacity of the fluid caused by the buttery particles. A few drops of the milk are introduced between two plates of glass, so set in an ocular tube that they can be brought close together or separated by means of a graduated screw, and thus en- close at their base a thinner or thicker stratum of milk. The observer then looks through the tube at a light set 3 ft. off, and gradually sepa- rates the plates of glass, increasing the depth of the layer of milk, till this at last becomes so opaque that the light is lost to view. The figure to which an index on the instrument then points refers to a table, upon which the corresponding quality of the milk as to quan- tity of cream is designated. As the large glob- ules of cream are the first to rise, if this is re- moved the remaining skim milk will contain only the smaller globules'; and this has been used in Germany as a means of ascertaining whether milk has been skimmed. Milk is easily adulterated by substituting various cheap materials for the natural ingredients, thereby seriously affecting its quality, while the fraud can be detected only by the skilful examina- tion of the chemist. The nourishing cream is removed and water is substituted. This in- volves the addition of white thickening sub- stances to disguise the cheat, and of other strange ingredients to restore or retain the sweetness and saltness of the milk. Large cities are almost hopelessly exposed to these frauds ; but worse than all, a large portion of the milk with which they are supplied is that of diseased cows kept in crowded stables and fed with cheap unwholesome food, especially the swill of distilleries. The evil became so serious that several years ago the attention of medical men in New York was directed to the subject, and in 1859 a careful investigation was made into the character and properties of the milk of cows fed upon the swill of distilleries, the results of which are embodied in a report of S. R. Percy, M. D., and published in the " Transactions of the New York Academy of Medicine," vol. ii., part iv. The following are some of the analyses of healthy and diseased milk in that report : 556 VOL. xi. 35 CON8TITU- 1. 2. 3 4. 5 6 7 g 98-0 1-8 87-7 1-9 Water... Butter. . . 86-261 86-86 4-40 4-42 85-6 4-7 87-0 ; 92-4 3-5 1-9 86-9 4-0 Sugar. . . 8-97 1-79 4-8 1-5 1-0 0-8 1-8 4-2 Caseine. . 5-71 7-OS 4-8 6-8 8-fi 8-4 7'4 4-4 Salts 0-66 0-85 0-6 1-2 1-1 1-0 1-7 0-5 Total... 100-00 100-00 100-0 100-0 100-0 100-0 100-0 100-0 No. 1 is the milk of a cow kept for family use in New York ; No. 2, of swill-fed cows from distillery stables in New York ; both the analy- ses are by Dr. Doremus. The following are by Dr. Percy: No. 3, country milk furnished by a dealer to customers in New York ; No. 4, milk as drawn from the cows in a Brooklyn distillery stable ; No. 5, sample of same deliv- ered to customers; No. 6, another sample of the same as sold to customers; No. V, milk from a sick cow, Brooklyn distillery stables; No. 8, sample of the milk used by Gail Bor- den for preparing the "condensed milk." Healthy milk was observed by Dr. Percy to have an alkaline reaction, while that from diseased animals was always acid. The same observation had been made by Gay-Lussac, Berzelius, and others ; and the effect is found to be induced in a short time in animals shut out from the light of day, and in those con- fined in bad air and supplied with bad food. In the analyses, the bad milk is at once recog- nized by its unduly large proportion of caseine, while the sugar and often the butter is as dis- proportionately small. The large amount of saline matter found in bad milk is caused by the addition of salt made for the purpose of disguising the adulteration with water. But the proportions of the ingredients, though suf- ficient to expose the character of the milk, cannot indicate the poisonous qualities of the worst sorts, nor the evil effects that may fol- low their use. In organic compounds, such as we use for food, as in the air we breathe, the most dangerous poisons may lie concealed be- yond the power of detection of the most deli- cate tests or the most powerful microscopes, and their existence is brought to light only by their effects upon the human system. Thus the real nature of the distillery milk is most properly shown in the report by citation of several cases of disease in young children traced directly to its use. Milk may be impure from natural as well as artificial causes. The microscope affords a pretty good test in both cases, starch granules and chalky particles be- ing easily detected, the latter especially on the addition of a little acid. The simplest cases of diseased milk are those caused by feverishness in the cow. This causes the globules to assemble in groups, as if they possessed a certain degree of vitality somewhat resembling that of blood globules. Fig. 2 shows the microscopic appear- ance of the globules in feverish milk. Fig. 3 gives the appearance of a sample of milk from a distillery stable in Brooklyn, examined by Dr. Percy. It was taken from a cow very ill