By a similar process of reasoning the two Dicks in America introduced an intradermal diagnostic test for scarla tina, the toxin being derived from broth cultures of a variety of haemolytic streptococcus found in the throats of scarlatina patients and believed by some to be the cause of the disease. So far the Dick test is not on such firm ground as the Schick test. Neverthe less some authors have expressed their view that the test is of much value in determining susceptibility or insusceptibility to scarlatina and that an anti-scarlatinal serum prepared by means of the haemolytic streptococci is in many instances efficacious in immunizing the Dick-positive individual and rendering him neg ative on subsequent intradermal tests. A further extension of the principle has been applied in the case of tuberculosis (q.v.), but the work is still in its earlier stages and the time is not ripe for dogmatic statement.
A hitherto unrecognized disease was described by McCoy in 1912 when investigating ground squirrels in Tulare county, Calif., that had been attacked by a plague-like disease not caused by B. pestis. Since that time it has been found widely in the United States and was definitely recognized as affecting man in 1914. Since 1914 tularaemia has occurred in at least nine laboratory workers engaged on investigations with B. tula reuse. The micro-organism is an exceedingly minute cocco-bacillus and it is believed that infection in man occurs by inhalation or by a blood-sucking fly. Transmission from rabbit to rabbit occurs by the rabbit louse and the rabbit tick, neither of which bites man.
During the war there occurred in Flanders amongst the men in the trenches a severe form of disease associated with jaundice and haemorrhage which was traced to a spirochaete similar to or identical with Sp. icterohaemorrhagica, which in Japan infects rats, and is transmitted by them to man. The same organism was found in the rats infesting the trenches.
A bacillus (B. acidophilus odontolyticus) has been isolated from carious teeth and in pure culture forms suffi cient acid to dissolve the enamel. Undecayed teeth placed in such pure cultures for a period of weeks show loss of enamel at spots and local growth of the bacilli along the dental tubules. Micro scopically the appearance of this artificial caries is identical with that of natural caries.
Numerous papers have been published upon botu lism, a form of severe food poisoning (q.v.) dependent upon an
anaerobic bacillus (B. botulinus). The nervous system is pro f oundly attacked by the toxin, difficulty of vision, dilated pupils, ptosis and paralysis being among the earliest symptoms. The toxin differs from other toxins in being pathogenic when admin istered orally ; it is absorbed in the stomach and upper duodenum. An antitoxic serum has been prepared and is useful in treatment. This form of food poisoning was originally associated with sau sages but occurs in connection with a great variety of foods. Most of the recorded cases have occurred in America.
In syphilis (see VENEREAL DISEASES), Brown and Pearce succeeded in transmitting the disease to rabbits by intra testicular inoculation and showed the close resemblance of the pathological and clinical manifestations to those met with in man. By a prolonged series of experiments on rabbits Pearce answered in the negative the long debated question whether yaws and syphilis are manifestations of a single disease. Much work has been done on the Wassermann reaction. All doubts are not set at rest nor is the behaviour of the reaction completely understood, but it has stood the test of time and is considered of great diagnostic value.
the investigation of spirochaetal diseases caution in deduction from experiment is shown by the fact that spirochaete-like bodies are to be found in the lateral ventricles of normal monkeys, rab bits and guinea-pigs. Only after animals that had been injected long previously with material from disseminated sclerosis (which is regarded by most authorities as of syphilitic origin) had been found to present these bodies in their lateral ventricles, was their existence in normal animals also discovered.
In typhus and trench fevers minute parasites were discovered belonging to the group now named Rickettsia. For a short time the relation of the Rickettsia to the disease was in doubt, but largely owing to the work of Bacot, an eminent en tomologist who contracted typhus during his investigations and died therefrom, it is now recognized that both diseases depend upon the presence of varieties of Rickettsia, and that these para sites are conveyed from patient to patient by body lice. One of the most delicate manipulative operations ever attempted, and actually carried out with brilliant success by Bacot, was the filling of the rectum and intestine of lice with Rickettsia-infected blood by means of a fine capillary glass tube.