Physiologists have not arrived at the explanation of all such facts; but much has been done by comparative anatomy to show that many of them are merely arrests of development, and cases of interference with the ordinary law. That, in fact, they show the mutual harmony and connection of the laws of nature to be such, that the development of any one law implies the concurrence, so to speak, of some other, just as the successful incubation of an egg, or any other familiar fact, implies the presence of certain conditions. We cannot boil a drop of water without the concurrence of various laws: we say it boils ordinarily at 212° of Fahrenheit; but how many conditions this involves! Until understood, how few could have guessed that mechanical pressure could have so modified the degree of heat necessary, as to exalt it to more than double, or reduce it to less than half; and again, how few would have looked for the force which, under common circumstances, governed the point at which water was thus converted into steam, in the pressure of the atmosphere; yet so mutually influential are these conditions—namely, heat and a certain pressure in modifying this change of form or matter—that some of Faraday's most interesting results in experimental chemistry (we allude to his reducing several gaseous bodies to the liquid form) were obtained by _abstracting_ heat and increasing pressure. It is of very great consequence to remember these interferences in relation to disease, because most diseases may be regarded as examples of them. Considered as "abstract wholes," as entities—diseases are necessarily unintelligible: but when looked at as natural processes obscured by interferences (if the inquiry be conducted with strict observance of those principles which are essential in all philosophical researches), they either at once become intelligible, or, at least, as open to investigation as any other facts in natural philosophy. When we investigate the laws of nature with a view to the development of the sublime objects of natural theology, the concurrence of the various conditions, necessary to the most ordinary phenomenon, inclose the most irresistible proofs, from natural evidence, of the Unity of the Creator. Regarded in the light of facts which we as yet may not be able to generalise, the cases here recorded by Abernethy are very interesting; although it is to be regretted that both cases were bodies brought in for dissection, in times when the circumstances baffled, if they did not forbid, any inquiry into the histories of them. It is lamentable to think of the state of the law with respect to Anatomy at that time. Any surgeon who was convicted of _mala praxis_, resulting from ignorance of Anatomy, was severely fined, perhaps ruined; and yet so entirely unprovided were the profession with any _legitimate_ means of studying Anatomy, that they could only be obtained by a connivance at practices the most demoralizing and revolting.