As I have written elsewhere in this tome, there were two important contributions that allowed those working in the field of parasitology to make breakthrough discoveries in the nineteenth and early twentieth centuries. The first was the microscope. It was the Dutch rug trader, Antonie van Leeuwenhoek, who began to develop and refine this technology in the seventeenth century. Robert Hooke, an early British microscopist and a contemporary of the resourceful Dutchman, created what was ultimately to evolve into one of the most powerful of all biological concepts, in fact, one that still is being cultivated today. While looking through one of his primitive scopes one day, Hooke noted that the structure of a piece of cork he had sliced was divided internally into what he called “cellulae”. With this observation, the cell theory was borne.

The contribution of van Leeuwenhoek provided the way for technology to eventually take us inside cells and build on Hooke's observation. The cell theory, along with Darwin's evolutionary theory, unquestionably did more to alter the biological landscape than any other conceptualization. There was, however, a widely held idea that had to be purged before significant biological research could progress.