THE SYRINGOTOME. 71 



to be easily grasped, and should be freed from sand and grit before 

 using. The larger and coarser kinds are useful in various ways. 



All sponges should be washed after using, and boiled occasion- 

 ally for a few moments. It is said that they may be freshened by 

 soaking in brine to which a little iodine has been added. 



161. Syringotome Fig. 15. This is sometimes called "can- 

 aliculus knife." It is a small, concave, blunt pointed bistoury, 

 which is very convenient for delicate work upon the brain and heart, 

 and for following and slitting up narrow canals. 



The syringotome was found very serviceable by the senior author in tracing out the 

 tortuous canals upon the heads of sharks and skates at the Museum of Comparative 

 Zoology in 1866-7. At his suggestion it was included in the set of dissecting instruments 

 supplied to the students of " The Anderson School of Natural History at Penikese Island " 

 in 1873. Excepting with the brain, however, most of the uses of the syringotome may be 

 subserved by the less expensive tracer. 



162. Tags. Two sizes of tags are needed : the smaller are for 

 numbers or brief memoranda sufficient to identify the specimen ; 

 they are used by stationers and dry goods dealers. The larger are 

 the smallest size of " Dennison's Shipping tag," and are 3.5 cm. wide 

 by 7.2 long; they should be provided with strings, and the eyelet 

 should be guarded by a metal ring. 



163. Tenaculum See Codman & Shurtleff, A, 42, Fig. 8. 

 This is seldom needed in felitomy. 



164. Tools, Carpenter's. A laboratory should contain the 

 ordinary tools, as saw, hammer, screw drivers, awls, bits and stock, 

 rat tail and three cornered files, screw hooks and eyes, etc. 



165. Towels. Excepting the roller towels, these should be 

 short. The finer crash is more expensive, but wears longer than 

 the cheaper stuifs, and there is less lint ; it may be had in rolls, 

 which may be cut into the desired lengths. 



166. Tracer Fig. 17. This is prepared from a piece of hex- 

 agonal or octagonal steel rod, about 15 cm. long, and 4 mm. in 

 diameter. The middle third is left as a handle ; one of the terminal 

 thirds tapers to a blunt point, and serves as a probe for some 

 purposes ; the other end tapers in like manner, and is bent at the 

 tip so as to form about the fourth of the periphery of a circle 1 cm. 

 in diameter ; the concavity is then sharpened. 



The value of the tracer in isolating vessels and nerves can hardly 

 be overestimated. A dull tracer may be used also in lifting Vessels 

 and nerves that have been isolated already, as in experiments. 



