What I want you to understand is that the difference between the communication of the poisons of these two classes of diseases is not in the poison, or in the nature of the poison, hut in the way in which the poisons leave the body of the infected person. I want you to come to the conclusion that the last mentioned diseases, cholera and typhoid fever, are just as essentially communicable diseases as scarlet fever and smallpox.

The diseases which are most obviously communicable have among them diseases which it is supposed every one must take. They are diseases that especially belong to children; the reason is that they are diseases which a person only has once in his life as a rule, So you see they especially affect children, because as soon as a child is exposed to the poison of one of the diseases he is most likely to take it, in which case he does not, as a rule, get it again later in life, and if he does not take it then, it is very likely that he will never have it at all The only one of these diseases that is no longer specially confined to children is the most dreadful of them - viz. smallpox, although it was formerly the most fatal disease of childhood, and killed half the children under ten years of age before vaccination was practised. It is now rare for a child who has been properly vaccinated to have smallpox.

The idea that children must have measles and whooping cough is an entire mistake. If these diseases do not kill children directly, they kill a very large number indirectly, and maim a great many more by leaving them liable to diseases of the respiratory organs; hence, if possible, children should be prevented from catching them. Many people will allow their children to take measles. I consider that they are wrong, and that they ought not deliberately to expose their children to that which may kill them; they have no business to assume that their children will get that disease, and must have it, and I am sure no child has ever been the better for having had it, while many are injured for life.

Now, all these diseases spread more where there is overcrowding, and so they always spread in large towns. You can understand, from the various ways in which these diseases spread, that they are more dangerous where people are crowded together, but this is especially true of typhus fever, which is only at home in very crowded parts of towns. It does not spread in other parts if it is introduced, and in fact the infective distance of typhus fever is very small. Although it is an extremely infectious fever it does not spread from one spot to another, through persons going occasionally to see the patient, nor does it attack the attendants if they do not handle the patient. It is a fever that was formerly known as jail fever, and was given other names, according to the overcrowded places in which it spread, and it is one of the diseases of which we are told that the poison can originate spontaneously.

We have been gradually reducing the number of diseases of which we believe the poison originates spontaneously. Now, typhoid, or enteric fever, has only been recently separated from typhus fever. It has been shown clearly that whereas typhus fever spreads especially in overcrowded places, and among the poor and destitute and starved, typhoid fever spreads, on the contrary, wherever the matters that are discharged from the intestines of human beings are not got rid of from houses or towns. The distinctive characteristics of these two diseases I will not enter upon, but they are so different that it is a perfect mystery to us now that they should ever have been confused. We have seen, too, the different ways in which these diseases spread.

We are told on very high authority that the poison of enteric fever is capable of originating de novo in filth of various kinds, that you only have to have a certain amount of decomposing matter under certain circumstances, and the poison of this disease can be produced and given to human beings. This statement is supported, too, by the assertion that in the majority of instances where cases of typhoid fever arise you are not able to find where it came from. Now, with regard to that, I would point out to you that it is a disease a person may suffer from for weeks, and with which he may go about from place to place without knowing that he has it. A person may go through it to the third stage, and then fall down dead with it, and the disease may be regarded as heart disease. Now, notice that wherever he has gone for the last three weeks he has been spreading the poison of typhoid fever.

These are a few facts which show you that it is a ridiculous impossibility to expect that we can trace the poison of this disease always to the place from whence it came. It may be mixed with milk in the Midland counties of England, sent up to London, and distributed to a number of houses in London. The connection between these may never be known, and there is no doubt that that method was never suspected until the recent epidemics of this disease occurred; and I put it to you whether we are in a position to say that we are able in a case of this disease to state that the poison was not derived from a previous case.