334 



SCIENCE 



[N. S. Vol. LIV. No. 1397 



is -full and authoritative. Hugh Cabot still 

 regards spinal anaesthesia as having a place 

 in surgery. 



The chapter on Poison Gas in warfare is 

 not solely of historic interest, because surgeons 

 on ambulances and those connected with in- 

 dustrial plants and chemical laboratories will 

 find much of practical importance. 



The final chapter on a most successful 

 method of dressing an artificial anus prepared 

 by the editor himself is in the form of a case 

 report and is the type of literature which is 

 of the greatest practical use to surgeons and 

 patients. 



The index of the system consists of four 

 " keys " ; first, each volume as it stands upon 

 the shelf carries a conspicuous label of the 

 general subject matter it contains; second, as 

 we open the book the table of contents is 

 quite complete; third, each volume has a 

 separate index; and finally, the complete index 

 of the entire eight volumes occupies 182 

 pages in the form of a desk volume and makes 

 it perfectly easy for one to find any reference 

 he may desire. Stuart McGuire 



SPECIAL ARTICLES 

 A NEW GRAPHIC ANALYTIC METHOD 



1. The graphic methods which deal with a 

 treatment of two or three variables are com- 

 monly based on a relation of the variables to 

 a system of rectangular cartesian coordinates. 

 If the equation is known the laws may be ex- 

 pressed in the customary way by the methods 

 of analytic geometry. 



If, however, we are confronted with a sys- 

 tem of two or more equations which are so 

 related to each other that the growth of one 

 will influence the growth of another (in a 

 negative and positive sense) the following 

 method will furnish a means of expressing 

 such movements in a concise form and in a 

 manner well adapted for the purpose of anal- 

 ysis. 



Suppose we have three general equations: 



x = f (a), y=.f (&), z = f (c), 



where the change of a will affect x as well 



as y and the change of h will affect y as well 



as z and if further / (a), / (h) and / (c) 

 are quotients expressed: 



a a . b 



-T"! — and — ; 

 be c 



we have then : 



a a b 



6 c c 



and notice that each quotient or independent 

 variable is related to the other independent 

 variable by the possession of one of its alge- 

 braic members. 



If a number of equations which have a re- 

 lationship of this nature is brought into a 

 system of positive coordinates as shown in 

 Fig. 1, the four quadrants and the coordinates 



Fig. 1. 



forming them may be named in the following 

 manner : 



I. Quadrant a h 



II. Quadrant a c 



III. Quadrant c c 



IV. Quadrant c h 



Therefore the ordinates of each quadrant will 

 have two different coordinates or scale values 

 with the exception of the third or neutral 

 quadrant which axes have the same scale val- 

 ues c and are acting in a translative sense ro- 

 tating the value c 90° to bring it in the third 

 and last relationship with value h, in the 

 fourth quadrant. 



