(2) Extract of frambœsia material, free from all organisms other than T. pertenue, reproduces the disease if inoculated.
(3) Extract of frambœsia material deprived by filtration of T. pertenue is no longer infective on inoculation.
The method of infection is contaminative, by direct contact. Women in Ceylon are frequently infected by their children. Any slight skin abrasion is sufficient to admit the parasite. In some cases, insects may carry the disease from person to person, and even in hospitals, when dressings are removed, it has been noticed that flies greedily suck the secretion from the ulcers. T. pertenue has been recovered from flies that have fed on yaws, and monkeys have contracted the disease when flies were placed and retained on them for a short time, after the insects had fed on yaws material.
Cultivation.—T. pertenue has been cultivated by Noguchi, who finds three types of parasites in his cultures, as before mentioned. Its multiplication is by longitudinal division.
Noguchi[169] (1912), has cultivated species of Treponema from the human mouth, e.g., T. macrodentium, T. microdentium and T. mucosum, the latter from pyorrhea alveolaris. These parasites in the past may have been confused under the name Spirochæta dentium.
Class III. SPOROZOA, Leuckart, 1879.
The third group of the Protozoa consists entirely of parasitic organisms forming the class known as the Sporozoa or spore-producing animals. The members of this class are characterized by possessing very great powers of multiplication, coupled with a capacity for producing forms that serve for the transference of the organisms to other hosts. These reproductive bodies, whether for increase of numbers within one host or for transmission to another host, are called spores. But, strictly, the term spore should be used only in the latter connection, when a protective or resistant coat known as a sporocyst envelops the body of the spore.
The Sporozoa are widely distributed, occurring in various tissues and organs of Annelids, Molluscs, Arthropods, and Vertebrates. Their food, which is fluid, is absorbed osmotically. The life-cycle of a Sporozoön may be completed within one host or may be distributed between two different hosts.
The Sporozoa were divided by Schaudinn into two groups or sub-classes, called (1) the Telosporidia, and (2) the Neosporidia.
The Telosporidia are Sporozoa in which the reproductive phase of the parasites is distinct from the growing or trophic phase, and follows after it. The Neosporidia include Sporozoa in which growth and spore-formation go on simultaneously. This classification is not final, for certain exceptions and difficulties are already known with regard to it. It is possible that the class Sporozoa is not a natural entity, but should be replaced by two classes of equal rank, corresponding in most respects with the Telosporidia and Neosporidia.