Note 836 — Chapter V · (continued 3)

Cullen, with that admirable candour which was one of the most attractive peculiarities of his fine intellect, confesses his want of acquaintance with the microscope: ‘It leaves me, who am not conversant in such observations, altogether uncertain with respect to the precise nature of this part of the blood.’ Cullen's Works, vol. i. p. 195. A pathologist without a microscope is an unarmed man, indeed. In regard to his animal chemistry, one passage may be quoted as a specimen of the manner in which he arrived at conclusions speculatively, instead of subjecting the phenomena to experimental investigation. ‘We may remark it to be highly probable, that all animal matter is originally formed of vegetable; because all animals either feed directly and entirely on vegetables, or upon other animals that do so. From hence it is probable, that all animal substances may be traced to a vegetable origin; and therefore, if we would inquire into the production of animal matter, we must first inquire in what manner vegetable matter may be converted into animal?’ Cullen's Works, vol. i. pp. 177, 178. The therefore and the must, resulting merely from an antecedent probability, are characteristic of that over-boldness, into which deduction is apt to degenerate, and which is strongly contrasted with the opposite vice of over-timidity, by which inductive reasoners are tainted.