Not only are the ticks which have fed on infected individuals capable of conveying the disease to healthy animals but they transmit the causative organism to their progeny. Thus Möllers (1907), working in Berlin, repeatedly infected monkeys through the bites of nymphs which had been bred in the laboratory from infected ticks. Still more astonishing was his discovery that ticks of the third generation were infective. In other words, if the progeny of infected ticks were fed throughout life on healthy animals, and on maturity deposited eggs, the nymphs which hatched from these eggs would still be capable of carrying the infection. The developmental cycle of the spirochæte within the tick has not been fully worked out, though the general conclusions of Leishman (1910) have been supported by the recent works of Balfour (1911 and 1912), and Hindle (1912), on the life cycle of spirochætes affecting fowls. _Spirochæta duttoni_ ingested by _Ornithodoros moubata_ apparently disappear within a few days, but Leishman believed that in reality they break up into minute granules which are to be found in the alimentary canal, the salivary glands and the Malpighian tubes of the tick. These granules, or "coccoid bodies," as Hindle calls them, are supposed to be the form in which the spirochætes infect the new host. We shall see later that Marchoux and Couvy (1913) dissent wholly from this interpretation. According to Leishman, and Hindle, the coccoid bodies are not injected into the vertebrate host with the saliva of the tick, as are the sporozoites of malaria with that of the mosquito. Instead, they pass out with the excrement and secondarily gain access to the wound inflicted by the tick. Nuttall (1912) calls attention to the fact that the geographical distribution of _Ornithodoros moubata_ is far wider than our present records show for the distribution of the relapsing fever in man and that there is every reason to fear the extension of the disease. Huts where the ticks occur should be avoided and it should be remembered that in infected localities there is special danger in sleeping on the ground. EUROPEAN RELAPSING FEVER--There is widely distributed in Europe a type of relapsing fever which is caused by _Spirochæta recurrentis_. It has long been supposed that this disease is spread by the bed-bug and there is some experimental evidence to show that it may be conveyed by these insects. In 1897, Tictin found that he could infect monkeys by inoculating the contents of bed-bugs which had fed upon a patient within forty-eight hours. Nuttall, in 1907, in one experiment succeeded in transmitting _Spirochæta recurrentis_ from mouse to mouse by bites of bed-bugs. The bugs, thirty-five in number, were transferred at short intervals from one mouse to another, not being allowed to take a full meal on the first, or infected mouse.