Up to that time, although it had been shown that the rods or bacilli contained in the blood were living organisms and the cause of the disease, this did not explain the mode of infection; how the organisms contained in the blood passed to another animal, why the disease occurred on certain farms and the adjoining farms, particularly if they lay higher, were free.

Koch showed that in the cultures the organisms grew out into long interlacing threads, and that in these threads spores which were very difficult to destroy developed at intervals; that the organisms grew easily in bouillon, in milk, in blood, and even in an infusion of hay made by soaking this in water.

This explained, what had been an enigma before, how the fields became sources of infection.

The infection did not spread from animal to animal by contact, but infection took place from eating grass or hay which contained either the bacilli or their spores.

When a dead animal was skinned on the field, the bacilli contained in the blood escaped and became mingled with the various fluids which flowed from the body and in which they grew and developed spores.