SYMBIOSIS AND "VEGETATING ANIMALS." 811 



culm (as the coal-dust is technically called) with pitch into hlocks, 

 brick-shaped, weighing but fourteen pounds each. Anything tend- 

 ing to the utilization of what is now waste is of value, when we con- 

 sider that the amount of anthracite coal sent to market represents 

 but about four fifths of the quantity that is actually raised from the 

 earth, the balance being piled up in unsightly heaps. 



Many of the subjects which I have incidentally touched upon have 

 been so elaborately dealt with by specialists in papers before the 

 members of this society, that the ground has been taken from under 

 me, and I am but a gatherer and gleaner, summarizing, as it were, the 

 results of their descriptions. Although, in the period under review, 

 many of the waste products of manufactures, formerly thrown away, 

 have been made to serve a useful purpose, there is yet room for fresh 

 efforts in this direction, and the reward is certain. The manufacturer 

 who discovers a heretofore unknown use for the waste product of his 

 work necessarily cheapens the cost of the principal article of his pro- 

 duction, and thus secures an advantage over competitors. Much, as 

 we have seen, has already been done in this way, but there are many 

 other products which could be made under the direction of that mighty 

 converter, chemistry, to yield substances of use and profit. 



Science has taught us how to transmute the waste and refuse ma- 

 terials elements of pollution into sources of economy and wealth. 

 The utilization of the sewage of great cities for agricultural ends has 

 virtually been a demonstrated success in Paris and many of our own 

 towns. The same success, by patient experiment, is obtainable in 

 many other waste products, which, in ignorance of their value, we 

 suffer to defile our streets, pollute our rivers, and taint the air we 

 breathe. The purification of the outflow of paper-mills and the utili- 

 zation of the sludge and other waste products are now carried out. 



It would have been impossible, in the limits of this paper, to refer 

 in detail to more than a few of the principal examples of the success- 

 ful use of refuse. But those enumerated will serve to show to how 

 great an extent civilization is daily adding to the useful products of 

 the world, both by economizing its resources and by calling forth new 

 ones with the aid of chemistry. 



SYMBIOSIS AND "VEGETATING ANIMALS." 



A REVIEW. 

 Br W. T. SEDGWICK, Pn. D., 



A8SOCIATE IN BIOLOGY, JOHNS HOPKINS rNIYERSITT, BALTIMORE. 



SINCE the publication of the interesting observations and specula- 

 tions of Dr. Karl Brandt concerning the occurrence of chlorophyl 

 in animals, of which a summary account was given in a recent num- 

 ber of this periodical, under the heading "A Partnership of Plant 



