protein used to generate the antibody gave the strongest reaction, related proteins could give lesser reactions. This finding was developed by Nuttall into a quantitative method in which the amount of precipitate was measured. Using serum from a wide variety of animals he was able to show that the degree of immune reaction between species indicated the relationship between them. In a major work Blood immunity and blood relationship Nuttall and his colleagues presented the data from over 16,000 tests with serum from a wide range of animal species, both vertebrate and invertebrate. This work was the starting point for the field of molecular evolution. Arthropods as disease vectors In 1900 Nuttall and Austen published a book reviewing the evidence for transmission of disease by Insects, Arachnids and Myriapods, which included a discussion of the mosquito theory of malaria. Malaria had formerly been common in England, but few if any cases still occurred in 1900. Nuttall and colleagues carried out a survey of the distribution of the Anopheles mosquito in England, showing a concentration in the areas where malaria (ague) had previously been prevalent. The study suffered from the limitation of not distinguishing between the various species of mosquito, but its presentation, including maps, was one of the first of its kind. Nuttall and Shipley subsequently published a series of papers in The Journal of Hygiene on the structure and biology of Anopheles (1901–1903), which represented the most detailed study on the topic up to that time. Nuttall began working on ticks and tick-transmitted diseases in 1904. His first studies were with canine piroplasmosis. Piroplasmosis, or babesiosis, unknown in Britain, is a malaria-like disease caused by a protozoan parasite. At one stage in its life-cycle the parasite is pyriform (pear-shaped), hence the name piroplasmosis. It affects a wide variety of wild and domestic animals. Human cases occur, but are uncommon. Smith and Kilborne identified the parasite in Texas cattle fever, and established that it was transmitted by ticks, the first proven case of arthropod disease transmission. In a series of papers published with Graham-Smith in The Journal of Hygiene (1904–1907) Nuttall described the nature of the disease and the multiplication of the parasite in the blood of dogs. Subsequent work with Seymour Hadwen led to the discovery that trypan blue was an effective treatment both in dogs and cattle. This was a finding of great economic importance, and trypan blue