the argument continues and picks up pace a few sentences after

For the first time in history doctors could measure their efficiency against scales which they themselves had devised. This progress was due to a new perspective of the origins of some ancient scourges; water could be purified and infant mortality lowered; rat control could disarm the plague; treponemas could be made visible under the microscope and Salvarsan could eliminate them with statistically defined risks of poisoning the patient; syphilis could be avoided, or recognized and cured by rather simple procedures; diabetes could be diagnosed and self-treatment with insulin could prolong the life of the patient. Paradoxically, the simpler the tools became, the more the medical profession insisted on a monopoly of their application, the longer became the training demanded before a medicine man was initiated into the legitimate use of the simplest tool, and the more the entire population felt dependent on the doctor.