Identification of the consequences of such a complex phenomenon as longdistance trade has engaged historians of east Africa most particularly since the publication of Reginald Coupland's East Africa and Its Invaders (1938) and The Exploitation of East Africa (1939). The more critically long-distance trade is examined, the more dimensions emerge which appear essential for an evaluation of its impact. Studies made in the 1960s examined political consequences of the trade within and among African societies, as well as those economic aspects which affected African rulers (Roberts, 1968; Gray and Birmingham, 1970). More recently there has been a desire to assess the economic consequences to the vast majority of east Africa's population-not just upon the rulers-during the nineteenth century (see Alpers, 1973). The direction of inquiry is certainly welcomed. It, in turn, will no doubt lead investigators to a number of social and religious issues heretofore unexamined; other significant effects of the trade will be identified and their impact at least partially assessed.

One such consequence worthy of consideration is the disease factor. At present we know precious little about the introduction of epidemic diseases into the east African interior during or before the nineteenth century. The most valuable single work available is Dr. James Christie's Cholera Epidemics in East Africa (1876). As a resident physician on Zanzibar, Christie observed and described the effects of cholera on various social and ethnic groups within Zanzibari society. He also endeavored to trace the relentless spread of four specific cholera epidemics from the Asian sub-continent into eastern Africa. Christie, however, was unable to provide precise information about African mortality from cholera within the interior, although impressionistic statements are cited. Given the east Africans' lack of immunity to cholera, there is every reason to assume that its effects were devastating on all people exposed to it (Curtin, 1968: 195). As Christie painstakingly described, cholera was inadvertently transmitted by traders seeking ivory along specific caravan routes through the interior of eastern Africa. Disease and long-distance trade thus became inextricably linked, with caravans serving as an effective mechanism for transmitting alien epidemic diseases as well as indigenous diseases.