76 



NA TURE 



[November 26, 1891 



little practice. It may, perhaps, be doubted whether 

 specialists do not commonly underrate the difficulties in 

 diagnosis of these forms to an amateur, but Mr. Cooke 

 can at least be felicitated, on having made the dis- 

 tinguishing characters as clear as popular language 

 admits. 



In addition to the chapters on edible fungi, there is an 

 interesting one on poisonous species, which may convince 

 the reader of error in supposing that these are so 

 numerous as is vulgarly supposed. The fact is, we know 

 very little about the poisonous forms. Some few are 

 thoroughly established as poisonous, and great care 

 should be exercised by amateurs in view of this fact ; but 

 by far the rhajority of toadstools are simply not known to 

 be edible. The following paragraph, from p. 208, may be 

 worth quoting : — 



" Over and over again have we been urged to lay 

 down some rules, or instructions, whereby poisonous may 

 be distinguished from innocuous fungi. As often have we 

 declared, as we do now, that such general instructions 

 are impossible. No rules can be given whereby a poi- 

 sonous can be distinguished from a harmless species, 

 nothing except knowledge and experience. The poi- 

 sonous species already known are known because they 

 have a past history which has condemned them, and not 

 from any evidence written upon them. The most experi- 

 enced mycologist cannot tell by any character, feature, or 

 behaviour, that this or that fungus is poisonous or the 

 reverse. He only knows its antecedents and the company 

 it keeps. A large order of flowering plants, such as the 

 Solanacece, may be looked upon with suspicion ; but the 

 potato and tomato are not poisons. In the Agarics the 

 sub-genus Amanita, with warted caps, have always been 

 regarded with suspicion because of Agariciis miiscarius 

 and Agaric us phalloides ; but two others of the same 

 group, Agariciis rtibcscens and Agaricus strobiliformis , 

 are most excellent food." 



This, in spite of traces of obscurity, may be taken as sound 

 talk, showing an appreciation of the position by the author, 

 who is, moreover, quite alive to what generalizations can 

 be made as to the dangerous character of pink-spored 

 genera, and the bright red forms of Agaricus and Russula, 

 and so on ; and we recommend this chapter of warnings 

 to all who are inclined to taste rashly. 



The printing of the text and illustrations is decidedly 

 good, and we regard this little work as a gain to the 

 popular naturalist's library. 



"EXTENSION" PSYCHOLOGY. 

 Psychology : a Short Account of the Human Mind. 

 By F. S. Granger, M.A. (London : Messrs. Methuen 

 and Co., 1891.) 



THIS little volume, which forms one of Messrs. 

 Methuen's " University Extension Series," is not 

 a mere compilation from larger works on psychology. 

 Short as it is, it presents an independent development of 

 the subject ; and it is not infrequently characterized by a 

 freshness and vigour most helpful to the student. We 

 feel sure that Mr. Granger's short account of the human 

 mind will be a most useful little book in the " psychology 

 circles " of that National Home-Reading Union to the 

 existence and work of which Dr. Kill drew attention in a 

 recent issue of Nature. And few subjects are better 

 suited than psychology for study in this way. 

 NO. I 152, VOL. 45] 



Mr. Granger lays great stress on the essential unity of 

 the wave of consciousness that in its onward course con- 

 stitutes our mental life. By introspection (which is also 

 retrospection) we may analyze the waves that have 

 passed ; we may find elements of cognition, of feeling, 

 and of will ; we may separate out dominant and sub- 

 dominant ideas, sensations from without the body and 

 from within. But in the wave as it passes all these are 

 fused into one state of consciousness from which no one 

 of the constituent elements could be omitted without 

 destroying its identity. Students are only too apt to 

 fancy that the elements reached by psychological analysis 

 have a reality more real than the state of consciousness 

 with which they started. Mr. Granger does his best to 

 help them to avoid this fallacy. 



Welcome as the little book is from its independence of 

 treatment, it shows signs of hurried composition. Apart 

 from bits of sheer carelessness — e.g. where Mr. Granger 

 speaks of " the facts with which we have to deal in "— 

 the statements are occasionally ambiguous or misleading 

 " The retina, for example, may be supposed to transform 

 all sorts of stimuli into sight impressions." That is not 

 well put. " The causes which give rise to states of mind 

 may be divided into states of mind and states of body. 

 Thus the sensation of red is due to alight-stimulus received 

 from some object by way of the eye. Here, a state of mind, 

 the sensation of red, is caused by a state of body — namely, 

 a change in the retina. All cases of this kind, in which a 

 mental effect follows upon a physical cause, are instances 

 of physical laws. On the other hand, states of mind are 

 very often due to previous states of mind," &c. This, 

 again, is awkward and misleading. The physical basis 

 of a " sensation of red " is found in certain molecular 

 changes in the brain ; and these may be induced by 

 changes in the retina (external origin), or by other 

 changes in surrounding parts of the brain (internal 

 origin). So far as the molecular changes which are the 

 basis of the "sensation of red" are concerned, whether 

 they be due to causes external to the brain or to causes 

 within the brain, they are alike "instances of physical 

 laws." Here, and elsewhere in the book, the fundamental 

 distinction between energy and consciousness, between 

 the physical and the psychical, is not brought out with 

 sufficient clearness. 



In his preface, Mr. Granger tells us that "the illustrations 

 are largely drawn from every-day experiences and familiar 

 books." If the following illustration correctly represents 

 Mr. Granger's every-day experiences, Nottingham must be 

 a somewhat dangerous place to live in. " A group of ideas 

 may come into the mind, and by the process of associa- 

 tion may bring up an idea of some movement or series of 

 movements which is forthwith realized. The sight of a 

 stranger leads to the idea, and then to the act, of throwing 

 half a brick at him." Even if the experience is of every- 

 day occurrence, it can hardly be regarded as a happy 

 illustration. C. Ll. M. 



OUR BOOK SHELF. 

 Arithmetical Exercises in Chemistry. By Leonard 



Dobbin, Ph.D. With Preface by Prof. Crum Brown. 



(Edinburgh : James Thin, 1891.) 

 This book is a short collection of problems dealing with 

 chemical changes, and such physical changes as are 



