THE CHEMISTRY OF COOKERY. 773 



force " thus : " We are at freedom to imagine the existence of a new 

 agent, and to give it an appropriate name, provided there are phe- 

 nomena incapable of explanation from known causes. We may speak 

 of vital force as occasioning life, provided that we do not take it to be 

 more than a name for an undefined something giving rise to inexplica- 

 ble facts, just as the French chemists called iodine the substance x, so 

 long as they were unaware of its real character and place in chemistry. 

 Encke was quite justified in speaking of the resisting medium in space 

 so long as the retardation of his comet could not be otherwise ac- 

 counted for. 



" But such hypotheses will do much harm whenever they divert us 

 from attempts to reconcile the facts with known laws, or when they 

 lead us to mix up discrete things. 



" Because we speak of vital force we must not assume that it is a 

 really existing physical force like electricity. We do not know what 

 it is ; we have no right to confuse Encke's supposed resisting medium 

 with the bases of light without distinct evidence of identity. The 

 name protoplasm, now so familiarly used by physiologists, is doubtless 

 legitimate so long as we do not mix up different substances under it, 

 or imagine that the name gives us any knowledge of the obscure ori- 

 gin of life. To name a substance protoplasm no more explains the 

 infinite variety of forms of life which spring out of the substance than 

 does the vital force which may be supposed to reside in the proto- 

 plasm. Both expressions are mere names for an inexplicable series of 

 causes which, out of apparently similar conditions, produce the most 

 diverse results." 



THE CHEMISTRY OF COOKEEY. 



By W. MATTIEU WILLIAMS. 

 XXVI. 



THERE is one more constituent of animal food that demands at- 

 tention before leaving this part of the subject. This is the fat. 

 We all know that there is a considerable difference between raw fat 

 and cooked fat ; but what is the rationale of this difference ? Is it 

 anything beyond the obvious fusion or semi-fusion of the solid ? 



These are very natural and simple questions, but in no work on 

 chemistry or technology can I find any answer to them, or even any 

 attempt at an answer. I will therefore do the best I can toward 

 solving the problem in my own way. 



All the cookable and eatable fats fall into the class of " fixed oils," 

 so named by chemists to distinguish them from the " volatile oils," 

 otherwise described as " essential oils." The distinction between these 

 two classes is simple enough. The volatile oils (mostly of vegetable 



