Was Consumption inherited?

The Centenary of Dr Sutherland’s speech Consumption: Its Cause and Cure occurs on 4th September 2017. Here is an excerpt in which he posed the question:

Is the illness inherited?

Which he then answered:

It is not. No child is born tuberculous; nay more, every child who acquires the disease is infected after birth. There is not even, in my judgment, an inherited predisposition, although in the past medicine has made more of predisposition than theology of predestination. Perhaps both were unhappy doctrines.

An important step in curing a disease is to discover its cause. Finding out whether it was infectious or an inherited condition was crucial to seeing whether one could prevent and cure it, or merely alleviate the symptoms and to try and remove the afflicted from the conditions in which it arose.

Each family unit was a small experiment in determining the answer, or so it seemed. The law prevented the wife and husband from being closely related, whereas the children were closely related to both their mother and father. If the wife was consumptive, and the disease was infectious, one would expect the both the husband and the children to show signs of infection. On the other hand, when the children, but not the husband, became consumptive the disease—or rather, an inherited susceptibility to it—would appear to be transmitted by genes, not by germs.

…it was but natural that a belief should have arisen in an inherited predisposition without which the malady could neither arise nor spread. For consumption appears more frequently in the children than in the husband of a tuberculous woman. Both children and husband are exposed to the same infection: but, so they reasoned, the children have an inherited predisposition which is absent in the husband, and this they are prone to develop the disease. This argument, at first glance clear and convincing, is nevertheless fallacious.

The disease was infectious. When the immune systems of the husband and the children were exposed to the disease, the under-developed immune systems of the children were overwhelmed more quickly.

A child is reared by a mother with advanced disease and no precautions are taken. She coughs, and the air in her immediate vicinity is laden with droplets of secretion containing tubercle bacilli.  This air the child breathes.  Millions of bacilli are deposited on the skin and clothing, and are carried to the mouth by the hands. Again the mother kisses the child and the germs are swallowed.  She prepares the food and drink , handles it and coughs over it.  Everything, including the table utensils, is infected, and the child swallows human infection at every meal.  Such children are inoculated in every way.  They are saturated with tubercle bacilli.

Dr Sutherland was not alone among doctors in believing that tuberculosis was primarily an infectious condition. He did however, publish his research on the issue in the British Medical Journal. While at least one “reform” eugenist, Caleb Saleeby, agreed with him, “mainstream” eugenists, including Sir James Barr and Professor Karl Pearson, did not.

The difference in viewpoint was crucial: For those who believed that tuberculosis was an infectious disease, the approach was to preventing and curing infection and ensuring that living conditions were not favourable for it. For those who saw it as an inherited condition, the approach was to let nature take its course and to breed out the tuberculous.

Consumption: Its Cause and Cure is the publicly visible point at which Dr Sutherland’s disagreement with eugenists, which had up to that time been on medical and scientific grounds, had changed to the moral and political spheres as well.