52 REPORT— 1870. 



recently, and had only imperfectly united ; they contained an unusual amount of 

 fat. Portions of the ribs were removed and freed from fat before they were sub- 

 mitted to analysis, and the remaining portions were handed to the Curator of the 

 Museum of the School of Medicine. 



V. For comparison with these, I give' the composition of the femur and tibia of 

 a nine mouths foetus in column V., and of the bones from a case of osteomalacia 

 in column VI. 



VII. is calculated from the analysis of a healthy adult tibia by Valentin. 



VIII. is calculated from analyses of ribs of a healthy man, aged 25, by Von Bibra. 

 It will be observed that the ratio of organic constituents to earthy matter is 



much greater, while the ratio of lime to phosphoric acid is distinctly less, in the 

 ribs of paralytics than in those of healthy adults. There are the same differences 

 between the composition of healthy ribs and those of paralytics as between the 

 composition of the adult large bones and those of the fcetus ; and, generally, the 

 composition in cases of par.ilj'sis approaches that observed in cases of osteomalacia. 

 Whether the defects in the ribs of paralytics are due to arrested development or to 

 degeneration of the fully developed bone, it will require further experiments upon 

 carefully selected cases to prove; but from the evidence already obtained the 

 author was led to conjecture that both causes will be found to operate. 



The result of the analysis is suggestive rather than conclusive as to the condition 

 of the bones in patients the subj ects of general paralysis ; and it would be unsafe to 

 generalize from a few examples. The analysis, however, is a first instalment 

 towards determining, by scientific inquiry, whether the statements that have been 

 made, as to the peculiar liability to fracture of the bones in certain forms of 

 insanity, holds good as a general rule. 



On a Spectroscope in tvJiich the Prisms are automaticalh/ adjusted for the Mi- 

 nimum Angle of Deviation for the particular Hay under examination. Bi/ 

 JonN Browning, F.ll.A.8. 



In spectroscopes of oniinary construction, when several prisms are employed, a 

 great deficiency of light will be noticed towards the more refrangible end of tlie 

 spectrum. 



This arises from the fiict that the prisms are adjusted to the minimum angle of 

 deviation for the most luminous rays, which are near the other end of the .•spectrum. 



The Diagram shows the method in which the change in the adjustment of the 

 prisms to the minimum angle of deviation for each particular ray is made automa- 

 tically. In this diagram P, P, &c. represent prisms. All these prisms, witli 

 the exception of the first, are unattached to the plate on which they stand— 

 the triangular stand, on which the prisms are hinged together at the angles cor- 

 responding to those at the bases of the prisms ; to each of these bases is attached 

 a bar B, perpendicular to the base of the prism. As all these bars are slotted, 

 and run on a common centre, the prisms are brought into a circle. This central 

 pivot is attached to a dovetail piece, two or three inches in length, placed on 

 the imderside of the main plate of the spectroscope, which is slotted to allow it 

 to pass through. On mo^•ing the central pivot the whole of the prisms are moved, 

 each to a dift'erent amoimt, in proportion to its distance in the train from the first 

 or fixed prism, on which the light from the slit falls after passing through the col- 

 limator C. Thus, supposing* the first prism of the train from C, represented in the 

 diagram, to be stationary, and the second prism to have been moved through 1° by 

 this arrangement, then the third prism will have moved through 2°, the fom'th 

 through 3°, the fifth through 4^, and the sixth through 5°, As these bars are at 

 right angles to the bases of the prisms, and all of them pass through a common 

 centre, it is evident that the bases of the prisms are at all times tangents to a 

 common circle. 



Now for the contrivance by which this arrangement is made automatic. A lever 



L is attached to the corner of the triangular plate of the last prism ; this lever, by 



its further end, is attached to the support which carries the telescope through 



which the spectrum is observed. Both the telescope and lever are driven by the 



* It really has a slight movement round one angle. 



