REVIEWS. 91 



rather, perhaps we should say, of views arranged in suc- 

 cessive strata, like a geological formation. Sometimes the 

 successive views are very contradictory, and sometimes the 

 contradiction hardly seems to have been perceived by the 

 author; the latter portion having been tacked on without 

 rewriting the original text. But this is probably unavoidable 

 in a book which has been patched and altered so many 

 times. 



It is an unfortunate peculiarity of histology that so little 

 appears to be positively established, and so much is a matter 

 of " views." The fact appears to be that observers do not, 

 after all, differ so much as to the phenomenon itself as in 

 their interpretations of it. If they confined themselves to 

 stating precisely what can be seen, there would be little or 

 no controversy. But there is little chance of this happy 

 unanimity ever being attained, for several reasons. In the 

 first place, many phenomena are in themselves, strictly 

 speaking, ambiguous, with our present means of obser- 

 vation. There is a certain limited number of possible 

 explanations, each of which has certain points in its favour, 

 but no one of which can be absolutely proved. Then, again, 

 no one is content with a mere description of the phenomenon, 

 because a mere appearance without any attempt at interpre- 

 tation has no interest for us. We do not want to know about 

 black shadows and dots, but about what the shadows and 

 dots may be supposed to mean. So that histological contro- 

 versy is not likely to come to an end just yet. 



A remarkable illustration of the ambiguity of appearances 

 is afforded by the changes of opinion with respect to so well- 

 known a tissue as voluntary muscle. These are Avell 

 illustrated in Professor Frey's work. He gives, first, a very 

 clear statement of what were once two rival theories as to the 

 ultijnate composition of the muscular fibre (though the former 

 of them can hardly be regarded as a rival now), viz. the 

 theory that fibrillae are the pre-existing essential elements of 

 the fleshy mass ; and Bowman's view, which regards it as 

 made up of " sarcous elements." The latter conception has 

 very naturally the preference, since it has certainly commanded 

 the suffrages of most recent observers ; and when compared 

 with the fibrillar theory, it appears plain that only the 

 authority of some popular teachers and writers of text-books 

 could have given the latter so much acceptance as it had at 

 one time, especially in Germany. Professor Frey gives a 

 very good account of the further developments which the 

 conception of sarcous elements has undergone in the hands 

 of Krausc, Hensen, and others, the history of which appears 



