When the ticks were incubated at 21° to 24° C. no spirochætes, as such, were seen in the organs, except perhaps in the gut, where they often disappeared in a few days. When the ticks were previously incubated at 35° to 37° C. for two to three days, spirochætes, as such, reappear in the gut, organs and hæmocœlic fluid. The infection proceeds, not from the salivary gland, but from the infective excrement, that is, from the thick, white material voided by the tick while feeding, usually towards the end of the meal. This Malpighian excrement passes into the wound caused by the bite, being greatly aided by the clear and more limpid coxa fluid, which bathes the under surface of the tick’s body, and mixes with and carries the infective excrement into the wound. Ticks remain infective for a long time. [Illustration: FIG. 55.--_Spirochæta duttoni_ and its coccoid bodies in the tick (_O. moubata_).--Mononuclear cells of the tick (_O. moubata_) containing (_a_) Spirochæte breaking up into coccoid bodies; (_b_) Similar tick-cell containing coccoid bodies or granules. Such mononuclear cells occur in various organs of ticks and in developing Malpighian tubules. (Original. From preparations by Fantham.)] The spirochætes in the gut of infected ticks divide by a process of multiple transverse fission into granules, which are composed of chromatin (fig. 54). These granules--sometimes known as coccoid bodies--are capable of multiplication. Leishman first found them in clumps inside the cells of the Malpighian tubules (_cf._ fig. 55). To summarize, when spirochætes are ingested by a tick, some of them pass through the gut-wall into the hæmocœlic (body) fluid. They then bore their way into the cells of various organs (fig. 55_a_) and break up into coccoid bodies. In this manner the granules find their way into the ovaries and ova, thus explaining how the young ticks are born infected. Inoculation of these chromatinic granules usually produces infection. Infective granules are also seen in the rudiments of the Malpighian tubules of embryo ticks. Bosanquet and Fantham (1911), independently, have shown that molluscan spirochætes also break up into similar granules or coccoid bodies. Gross has also demonstrated multiple transverse fission in molluscan forms. Marchoux and Couvy (1913) and Wolbach (1914) consider the granules or coccoid bodies to be degeneration products. This is unlikely (see below). Schuberg and Manteufel have found that certain _O. moubata_, perhaps 30 per cent. of the specimens of a given neighbourhood, may acquire a natural active immunity against infection with _S. duttoni_. _S. duttoni_, or a closely allied form (by some termed _S. novyi_), occurs in Colombia, and is spread by the tick _Ornithodorus turicata_. In Panama a similar spirochæte is probably spread by _O. talaje_. *Spirochæta gallinarum*, Stephens and Christophers, 1905 (= *Spirochæta marchouxi*, Nuttall, 1905).