197 
The cycle usually followed by small-pox is, however, 
shorter than this, and from the exemption of children from 
the excessive death rate by this disease, it would seem as 
though the protection alforded by infantile vaccination 
endures now for a shorter period than it formerly did. 
This surmise is in accordance with the facts recorded by 
Mr. Simon respecting the increase in the number of cases of 
successful re-vaccination in the Prussian army during the 
years 1813 to 1833. 
It points to some imperfection in the operation or to a 
possible deterioration in the quality of the lymph, owing to 
its transmission too constantly through the human subject. 
In any case, its cause is worthy of full and patient in- 
vestigation. 
The objections that I have ventured to bring against the 
details of Mr. Baxendelfs tables, also do not apply to his 
comparison of the gross mortalities of the two periods he has 
chosen. 
The almost stationary condition of the death-rate of the 
country during the last thirty years has been noticed by 
many who are interested in the public health, and who 
have been disappointed at not obtaining from the Registrar- 
General tables of total mortality, that proof they so much 
desired of the efficacy of their sanitary improvements. Mr. 
Baxendell, indeed, shows that all the zymotic class of dis- 
eases, with the single exception of small-pox, have some- 
what diminished; and by limiting the term ‘preventible’ to 
this class of disorders he is able to ascribe to sanitary 
measures the modicum of improvement represented by “ a 
saving of one life in every 134,” or ''a reduction of 017 
per cent, in the general death-rate.” 
At the risk of sacrificing even this small tribute to the 
value of sanitary work, I must, however, point out that this 
restriction of the term 'preventible’ is not usually recog- 
nised by the medical profession* The sanitarian claims 
