MILKSICKNESS OR TREMBLES
This disease, common to man and some of the higher animals, is characterized by a definite symptom-complex, the salient features being excessive vomiting and obstinate constipation accompanied usually by a subnormal temperature. Many cases result fatally. At the present time it is known to occur only rarely in some of the southern and central western states in this country, but during the period of pioneer settlement it was quite common in districts that are now seldom affected. A great many references to milksickness are found in the writings of the early travelers and physicians in the Middle West, one observer predicting that "some of the fairest portions of the West in consequence of the prevalence of this loathsome disease must ever remain an uninhabitable waste unless the cause and remedy can be discovered."
In certain regions it is estimated that "nearly one-fourth of the pioneers and early settlers died of this disease." The mother of Abraham Lincoln fell a victim to this malady in 1818 in southern Indiana.
The disease appears to be usually contracted in the first instance by grazing cattle or sheep that have access to particular tracts of land; "milksickness" pastures are, as a rule, well known locally for their dangerous qualities. Milksickness is communicated to man through the medium of raw milk, or b.u.t.ter and possibly of meat. Although some of the earlier observers make the statement that the disease is self-propagating and can be pa.s.sed on without limit from one animal to another, later experiments cast doubt on this view.[114]
Many different theories have been advanced to account for the origin of the disease. The belief that mineral poisons such as a.r.s.enic or copper might be taken up by grazing animals and eliminated in the milk finds no justification either in a.n.a.lytical or in clinical data. Many plants, known or suspected to be poisonous, have been accused of furnishing the substance that imparts the poisonous quality to the milk of animals suffering from trembles, but there is no agreement as to the responsible species. Feeding experiments with suspected plants have in no case given unambiguous results. While some facts have been supposed to indicate that living micro-organisms are the cause of milksickness, other facts are opposed to this view, and the most recent experiments in this direction did not lead to conclusive results.[115] The true cause of milksickness is at present quite unknown.
DEFICIENCY DISEASES
Although diseased conditions due to the absence rather than the presence of certain const.i.tuents in the food are not perhaps to be properly cla.s.sed as food poisoning, they may be mentioned here to ill.u.s.trate the complexity of the food problem. At least one disease,--pellagra--is attributed by some observers to the presence of an injurious substance or micro-organism in the food, and by others to the absence of certain ingredients necessary to the proper maintenance of life.
_Beriberi._--One of the best established instances of a disease due to a one-sided or defective diet is beriberi. This affection is prevalent among those peoples subsisting chiefly or wholly on a diet of rice prepared in a certain way. As a matter of trade convention milled white rice has long been considered superior to the unpolished grain. The process of polishing rice by machinery removes the red husk or pericarp of the grain, and a diet based almost exclusively on polished rice causes this well-marked disease--beriberi--which was for long regarded as of an infectious nature.[116] It has been shown that if the husks are restored to the polished grain and the mixture used as food the disease fails to develop. Experiments upon chickens and pigeons show that an exclusive diet of white rice causes in these animals a disease (polyneuritis of fowls) similar to beriberi, which likewise can be arrested or prevented by a change in diet. From such observations the conclusion has been drawn that in the pericarp of the rice grain there are certain substances essential to the maintenance of health and that their withdrawal from the diet leads to nutritional disturbances. The name "vitamin" has been given to these substances, but little is known about their chemical or physiological nature. In a varied diet vitamins are presumably present in a variety of foodstuffs, but if the diet is greatly restricted, some apparently trivial treatment of the food may result in their elimination. It is uncertain how many and how various the substances are that have been cla.s.sed by some writers under the designation vitamin. At least two "determinants" are thought to be concerned in the nutrition of growth, a fat-soluble and a water-soluble substance.[117]
_Pellagra_ is one of the diseases attributed to an unbalanced diet,[118]
and it has been suggested that the increased use of highly milled maize and wheat flour from which vitamins are absent may be responsible for the extension of this malady in recent years. Other observers, while admitting that a faulty diet may predispose to pellagra as to tuberculosis and other diseases, do not a.s.sent to the view that it is the primary factor.[119]
_Lathyrism._--The name lathyrism has been given to a disease supposed to be connected with the use of the pulse and the chick pea. Nervous symptoms are conspicuous and sometimes severe, although the affection is of a milder type than pellagra. The disease is said to be a.s.sociated with the exclusive or almost exclusive use of leguminous food and with generally miserable conditions of living. It is yet uncertain whether lathyrism is a deficiency disease like beriberi and possibly pellagra, or whether it is due to a mixture of foreign and poisonous seeds with the particular legumes consumed, or whether under certain conditions the legumes themselves may contain poisonous substances generated by some unknown fungus growths.
_Favism_ (from _fava_, "bean") is an acute febrile anemia with jaundice and hemoglobinuria which occurs in Italy and has been attributed to the use of beans as food or even to smelling the blossom of the bean plant.[120] A marked individual predisposition to the malady is said to exist. Although the symptoms are very severe and seem to point to an acute poisoning, no toxic substance has been isolated from the implicated beans. It has been suggested by some that bacterial infection, and by others that a fungous growth on the bean, is responsible, but no evidence has been brought forward to support either a.s.sumption.
_Scurvy_ in some forms is undoubtedly connected with the lack of certain necessary components of a normal diet. The development of scurvy on shipboard in the absence of fresh milk, fresh vegetables, fruit juice, and the like is a fact long familiar. Guinea-pigs fed on milk, raw and heated, and on milk and grain have developed typical symptoms of scurvy.[121] On the other hand, a form of experimental scurvy has been produced in guinea-pigs and rabbits kept on an ordinary diet of green vegetables, hay, and oats by the intravenous injection of certain streptococci.[122] The relative share of diet and infection in the production of human scurvy is consequently regarded by some investigators as uncertain.
_Rachitis_ or rickets is a pathological condition in some way connected with a protracted disturbance of digestion which in turn leads to faulty calcium metabolism. It does not seem probable that rickets is caused by too little calcium in the food, but rather by the inability of the bone tissue to utilize the calcium brought to it in the body fluids.
Experiments upon the causation of the disease have not given uniform results, and it does not seem possible at present to place responsibility for this condition upon any particular form of diet, such as deficiency of fat or excess of carbohydrates or protein. It appears to be true that the prolonged use of any food leading to nutritional disturbance causes an inability on the part of the bone cells to take up calcium salts in the normal manner.
While there are many obscure points with regard to the origin of both scurvy and rickets, there is no doubt that some dietary shortcoming lies at their base, and that they can be cured or altogether avoided by maintenance of suitable nutritional conditions.
THE FOODS MOST COMMONLY POISONOUS
Certain articles of food figure with special frequency in the reports of food poisoning outbreaks. It is not clear in all cases why this special liability to inflict injury exists. For an example, vanilla ice-cream and vanilla puddings have been so often implicated that some investigators have not hesitated to ascribe a poisonous quality to the vanilla itself. But there is no good evidence that this is the case, and it has been suggested that the reducing action of the vanilla favors the growth of anaerobic bacteria which produce poisonous substances, an explanation highly conjectural.
The conspicuous frequency with which the consumption of raw meat provokes food poisoning has already been set forth and in large part explained by the occasional derivation of meat from animals infected with parasites harmful to man. The even greater culpability of raw milk is due to the fact that milk is not only, like meat, sometimes obtained from an infected animal, but that it is a particularly good culture medium for bacteria, and in the process of collection or distribution may become infected through the agency of a human carrier. Foods such as ice-cream that are prepared with milk are also often connected with food poisoning. It seems probable that illness caused by ice-cream is much more commonly due to bacterial infection than to poisoning with metals or flavoring extracts. The responsibility of these latter substances is entirely problematic.
Cases of cheese poisoning, which apparently are relatively numerous, are of quite obscure causation. Whether such poisoning is due more commonly to some original contamination of the milk, or to an invasion of the cheese by pathogenic bacteria in the course of preparation, or to the formation of toxic substances by bacteria or molds during the process of ripening which the cheese undergoes, is left uncertain in the majority of cases.
Sh.e.l.lfish poisoning from eating oysters, mussels, or clams is unquestionably caused in some instances by sewage contamination of the water from which the bivalves are taken, and in such cases bacilli of the typhoid or paratyphoid groups are commonly concerned. It is a disputed question whether certain recorded outbreaks of mussel poisoning have been due to bacterial infection or whether sometimes healthy or diseased mussels taken from unpolluted water contain a poisonous substance. In a similar way it is uncertain whether a certain marine snail (_Murex bradatus_), sometimes used for food, contains under certain conditions a substance naturally poisonous for man, or whether it is poisonous only when it is infected or when toxigenic bacteria have grown in it.
Potato poisoning has been attributed in some cases to bacterial decomposition of potatoes by proteus bacilli; in other cases, to a poisonous alkaloid, solanin, said to be present in excessive amounts in diseased and in sprouting potatoes. It is noteworthy that many instances of potato poisoning have been connected with the use of potato salad which had stood for some time after being mixed, so that the possibility of infection with the paratyphoid bacillus or other pathogenic organisms cannot be excluded. That solanin is ever really responsible for potato poisoning is considered doubtful by many investigators.
These examples are sufficient to show that in a considerable proportion of cases of alleged food poisoning there is a large measure of uncertainty about the real source of trouble. Although the trend of opinion has been in the direction of an increased recognition of the share of certain bacteria, especially those of the paratyphoid group, there is an important residue of unexplained food poisoning that needs further skilled investigation. It is one of the objects of this book to point out this need and to draw attention to the numerous problems that await settlement. The first step is the regular and thorough investigation of every food poisoning outbreak.
FOOTNOTES:
[114] Jordan and Harris, _Jour. Infect. Dis._, VI (1909), 401.
[115] _Ibid._
[116] E. B. Vedder, _Jour. Amer. Med. a.s.soc._, LXVII (1916), 1494.
[117] McCollum and Davis, _Jour. Biol. Chem._, XXIII (1915), 181.
[118] Goldberger, _Jour. Amer. Med. a.s.soc._, LXVI (1916), 471.
[119] MacNeal, _Jour. Amer. Med. a.s.soc._, LXVI (1916), 975; Jobling, _Jour. Infect. Dis._, XVIII (1916), 501.
[120] Gasbarrini, _Policlinico_, November 14, 1915; abstract, _Jour.
Amer. Med. a.s.soc._, LXV (1915), 2264.
[121] Holst and Frolich, _Jour. Hyg._, VII (1907), 619; Moore and Jackson, _Jour. Amer. Med. a.s.soc._, LXVII (1916), 1931.
[122] Jackson and Moody, _Jour. Infect. Dis._, XIX (1916), 511.