Leichtenstern observed likewise: “In large families the contagious character of influenza is evidenced by the fact that the other members of the family become sick one after the other following the first case. This rule of succession is most easily seen in the early or late period of an epidemic and is less noticeable at the height, where the opportunity for all the members of the family to acquire the influenza outside the home is enormous. This latter fact explains why, when all sicken at once, the disease appears to be miasmatic in origin. There are many examples where other members of a family living with a sick individual remained unaffected. Parsons reports such cases, and this was so frequently the case that some British physicians state that it is the rule that there is but one case in a family or that the cases are widely separated in time. This was only partly true during the period of the pandemic and was very frequent in the epidemic following it. In this respect influenza acts like the common contagious diseases, diphtheria, scarlet fever, measles, etc., while the difference lies in the short incubation period and the very high contagiousness of the disease.” That West, in England, had observed the same phenomenon is indicated by the following quotation: “How is it, for instance, that one member of a household may be picked out and the others escape, though they are susceptible, as is shown by their acquiring the disease shortly after in some other way?” Again Leichtenstern wrote: “It is noteworthy that influenza on ships usually did not occur explosively, but spread gradually, and on ships usually lasted several weeks, as on the Bellerophon, from the 27th of March to the 30th of April; on the Canada from the 11th of April to the 24th of May; on the Comus from the 10th of April to the 3d of May. “The German Marine Report states, ‘Everywhere on the ships the disease began not suddenly but gradually.’ The frigate Schwalbe first had a large number of cases only on the 6th day after the beginning of the epidemic. There are, however, some exceptions, where the disease has begun suddenly with the greatest violence on ships as on land. Such was true of the frigate Stag which on the 3d of April, 1833, neared the influenza infected coast of Devonshire, and as it came under the land wind the epidemic suddenly broke out with great violence. Within two hours forty men took sick. Within six hours the number had increased to sixty. Within twenty-four hours 160 men were sick. As Parkes has remarked the evidence is insufficient that there had been no communication with the coast. There have been other examples of sudden outbreaks on ships, as on a Dutch frigate in the harbor of Mangkassar, where 144 men out of 340 took sick in a few days (1856); on the Canopus (1837) in the harbor of Plymouth, where on the 15th of February three-fourths of the men took sick with influenza.”