The most powerful cause of all, however, was, undoubtedly, the overpowering instinct of self-preservation, or, in other words, the need of working, no matter under what conditions, for the only means of obtaining food for themselves and their families. That, as a rule, necessitated their being near the work to be done--and rather than lose that work any conceivable hardship or abomination would be put up with. Another of the great causes of overcrowding was high rent. "It must not be imagined," wrote the Medical Officer of Health for the Strand (1858), "that this system of overcrowding is altogether a direct consequence of a state of poverty. It certainly does not appear to be so, for among the Metropolitan Districts the Strand ranks seventh in order of wealth. "The overcrowding seems to be partly a result of the high rental which the houses and rooms of many parts of the district--so peculiarly well situate for business purposes--command, and partly of the 'middleman' system, in which so many of the houses in the occupation of the poorer residents are let. "The 'middleman' system, which obtains so largely in this metropolis, in the letting of houses of the kind referred to, is ruinous in its action upon the working classes. The rent paid for a single room often exceeds a sixth or fifth of the total income of the family...." In a case in Bow Street Police Court it was given in evidence that 21, Church Lane, St. Giles', was rented of the owner for £25 a year--that the rents recovered from the sub-tenants were £58 10s.--and the rents received by these sub-tenants from lodgers £120 per annum.[65] Overcrowding was not confined to the sleeping places of the people, for the same causes which cramped the available space for people at night, cramped also the space for very many of them during the day when they were away from their so-called homes. Of the overcrowding in factories and workshops, where so many of the working classes spent their days, and of the insanitary conditions in which they there worked, no mention is made in these earlier reports of the Medical Officers of Health, not because there were not any, but because the inspection or regulation of factories and workshops did not come within the sphere of their duties. Evidence in plenty there is on this branch of the subject in later years from those who could speak with authority in the matter, and it will be referred to hereafter, and that the state of things then described is equally applicable to this period is an inference so legitimate as to be tantamount to a certainty. That the bad conditions under which the workers worked were a great contributing factor in the insanitary condition of the people is a fact as to which there can be no question.