Unfit Houses Captain W. BENN asked the Minister of Health if any estimate has been made of the number of houses occupied by the working classes that are likely to be closed under the Housing Act as unfit for human habitation during the next five years; and, if so, will he say what the estimate is? Mr. NEVILLE CHAMBERLAIN No such estimate has been made, but the following statement obtained from the Annual Reports of medical officers of health, so far as they are available, shows the action taken by local authorities in regard to the closing and demolition of houses under Sections 17 and 18 of the Housing, Town Planning, etc. Act, 1909, and Section 28 (1) of the Housing, Town Planning, etc. Act, 1919:of vaccine lymph are used for seed purposes in the Government lymph establishment; and, if not, what is the precise character and origin of the lymph or lymphs which are used for the purposes in question? Mr. CHAMBERLAIN I would refer the hon. Member to the answer given by my right hon. Friend the Minister of Labour to his previous question on this subject on the 13th December last. Mr. HAYDAY asked the Minister of Health what are the external evidences of a successful vaccination; what steps are taken by his Department to ascertain that public vaccinations are successful; and whether he can give any guarantee as to the length of time vaccination continues to remain successful? Mr. CHAMBERLAIN I am advised that the external evidence of successful vaccination is the production at the seat of inoculation of the characteristic and well-defined marks. As regards the second part of the question, the work of public vaccinators is periodically inspected by medical officers of my Department in order to secure that a high standard of public vaccination is attained. As regards the third part, the Royal Commission on Vaccination stated that the protection vaccination affords against attacks of small-pox is greatest during the years immediately succeeding the operation of vaccination; that it is impossible to fix with precision the length of this period; and that, though not in all cases the same, if a period was to be fixed, they thought it, might fairly be said to cover in general a period of 9 or 10 years.