84 Dr. Barry's reneived Inquiries concerning the 



recommended; because, from the ever-active condition of that 

 organ, its muscle is in a state which he regards as that of con- 

 tinued renewal ; and the fibrils are not so very difficult to sepa- 

 rate from one another. In no heart that the author has ex- 

 amined are the fibrils seen with more distinctness to be double 

 spirals than in the heart of the common frog. He has frequently 

 found such states of the fibril as those in fig. 3, and fig. 3 /, to 

 be seen with remarkable distinctness in muscle from the tail of 

 the Crawfish, Astacus fluviatilis. The observer should use for 

 examination the muscle of a healthy animal just killed, and never 

 employ muscle that has been preserved in spirit or in any other 

 fluid. The least degree of decomposition is sufficient to destroy 

 the spirals. Decomposing muscle presents granulated threads 

 enough (fig. 6 b), i. e. roM's of cell-germs, but rarely any trace 

 of spirals. (From this it is seen, and it is important to observe, 

 that the spiral threads are more easy of decomposition, and dis- 

 appear sooner than the formative cell-germs.) 



The accustomed eye can often discern spirals without a che- 

 mical reagent ; but for those unacquainted with them a reagent 

 is essential. The author provides two solutions ; the first a solu- 

 tion containing ^^o^*^^ ^^ corrosive sublimate in spirit of 0'940 

 spec, grav., and the second a concentrated solution of corrosive 

 sublimate in distilled water. Having placed a drop of the first 

 of these solutions upon glass, he introduces into it a minute 

 portion of muscle from the heart of the frog, and immediately 

 proceeds to carefullj^ spread it out with needles. He then sepa- 

 rates longitudinally a portion as minute as possible from the rest, 

 and teases this out in the same drop under a lens to the very utmost. 

 The threads thus prepared he removes to another strip of glass 

 upon which he had placed a drop of the solution No. 2, covers 

 them with a bit of the thinnest glass, and views them under the 

 microscope, — at first with a power of about 200 diameters, in 

 order to select the threads best adapted for observation, and bring 

 them into the middle of the field of view. He then applies a 

 power of about 600, and usually finds here and there a fibril 

 sufficiently separated from the rest at the edge of the preparation 

 to enable him to discern its spirals. It is not unimportant to 

 remark, that the muscle must always be first teased out in the 

 solution No. 1, before it is introduced into the solution No. 2 ; for, 

 besides corroding the needles, and making them quite useless, 

 the solution No. 2 instantly renders the substance of the muscle 

 so compact, that teasing of it out is absolutely impossible. Even 

 the solution No. 1 lays hold of the muscle to a certain extent, so 

 that the observer should proceed as soon as possible to apply the 

 needles. If it l^e desired to make preparations that are to be 

 preserved for any length of time, the concentrated aqueous solu- 



