ETIOLOGY AND PATHOGENESIS The exciting cause of scarlet fever has not yet been determined definitely. That the disease is of protozoon origin is a belief steadily gaining strength. Sponsors for this theory are Mallory, Duval, Siegel, Prowazek and Gamoleia. Mallory found the "Cyklasterion scarlatinale" in sections of the skin. Duval found these same bodies in the fluid of blisters artificially produced by means of ammonia. Rach and I have repeated Duval's work and can confirm his findings. Field, however, described similar findings as occurring in other conditions, thus casting some doubt on the correctness of Mallory's observations and making further study and investigation necessary. Similarly, the findings of Gamoleia (Chrysantozoon scarlatinte) lack confirmation.
It is a well-known fact that often after death from scarlet fever streptococci (according to )loser, in 60 per cent. of the cases) are found in pure culture in the throat, in all suppurative processes (lymph-nodes, ear), in the viscera, and in the blood. During life Joehmann succeeded in finding them only occasionally (21 times in 121 cases), and then only in fatal cases. Meyer, however, found streptococci in the less severe cases and such as terminated in recovery.
The majority of observers are of the opinion that this streptococcie invasion must be regarded as being secondary to an infection by some other as yet unknown organism. Others, however, consider them as being the exciting cause of the disease. They hold that the streptococcus scarlatinus represents a specific strain of coccus, which resembles other streptococci (erysipelas, puerperal fever, etc.) only morphologically. The chain of evidence is not yet complete because up to the present time it has been impossible to produce a scarlatinal infection, either in man or in animals, by means of pure cultures of the streptococcus. The endeavor to establish a relationship by means of complement binding or agglutinating substances in the blood serum has likewise failed.
Russian observers (Gabritschewsky and his scholars) have directed their efforts toward experimentally producing an abortive type of scarlet fever, with dead streptococci (streptococcus vaccines), and thus effect an active immunity, but thus far they have failed. It is worthy of note
in this connection to recall that so far as streptococci arc concerned, findings similar to those obtained in scarlet fever have also been noted in other infections, such as plague and variola. Furthermore, the fact that an attack of scarlet fever confers immunity is put forward as evi dence against the streptococcic nature of this disease, because in other streptococcus infections, such as erysipelas, an increased susceptibility to such infection is known to follow recovery.
However, regardless of any etiologic relationship that streptococci may have with scarlet fever, it is generally admitted by all observers that the course of the disease is materially influenced and the welfare of the patient correspondingly threatened by these various strepto coccus infections occurring in the course of scarlet fever.
So far as the virulence of the exciting cause of the disease, whatever that may be, is concerned, in none does the "genius epidemicus" play so large a role as in scarlet fever. In some epidemics the nature of the disease is an extremely mild one, with little or no mortality, while in others from thirty to fifty per cent. of the cases terminate fatally.
The portal of entrance of the exciting cause is problematical. Inas much as the first or initial symptom of the disease is usually redness and swelling of the pharynx, it is generally assumed that it is here that the infection takes its origin, and that, therefore, the pharyngeal affection is to be regarded as the primary one. Although the correctness of this assumption can only be proved by the discovery of the causative organ ism, many of the findings point in that direction, especially the occur rence of scarlet fever in wounds, and following burns. In such cases the exciting cause of scarlet fever evidently enters the body by some route other than the pharyngeal. It is to these atypical cases that the term "extrabuccal" scarlet fever is applied.