562 



SCIENCE. 



With the facts that are known in regard to the clinical 

 history of diphtheria and those which we have deter- 

 mined in our research, it is easy to make out a theory of 

 the disease which reconciles all existing differences of 

 opinion and seems to be true. 



A child gets a catarrhal angina or trachitis. Under 

 the stimulation of the inflammation products the inert 

 micrococci in the mouth begin to grow ; and, if the con- 

 ditions be favorable, the sluggish plant may be finally 

 transformed into an active organism, and a self-generated 

 diphtheria results. It may be, however, that by ap- 

 propriate treatment such a case is arrested before 

 it fairly passes the bounds of an ordinary sore throat. 

 Every practitioner knows that such diversity does 

 exist. Again, conditions outside of the body favor- 

 ing the passage of inert into active micrococci may exist, 

 and the air at last become well loaded with organisms, 

 which, alighting upon the tender throats of children, 

 may begin to grow and themselves produce violent an- 

 gina, trachitis, and finally fatal diphtheria. 



In the first instance we have endemic diphtheria as we 

 see it in Philadelphia ; in the second, the malignant epi- 

 demic form of the disease as it existed in Ludington. It 

 is also apparent that in the endemic cases the plant 

 whose activity has been developed within the patient 

 may escape with the breath, and a second case of diph- 

 theria be produced by contagion. It is also plain that as 

 the plant gradually in such a case passes from the mild 

 to the active state, there must be degrees of activity in 

 the contagium, one case being more apt to give the dis- 

 ease than is another ; also that the malignant diphtheria 

 must be more contagious than the mild endemic cases. 

 We think there is scarcely a practitioner who will not 

 agree that clinical experience is in accord with these log- 

 ical deductions from our experimentally determined 

 premises. 



It yet remains for us to investigate as to what are the 

 conditions outside of the body which will especially 

 favor the production of active micrococci, and also to 

 study the effects of agents in killing these organisms ; 

 for it is very apparent that local treatment of the throat 

 must often be of the utmost importance, and that it will 

 be far more effective if it be of such character as to kill 

 the micrococci, and not simply be anti-phlogistic in its 

 action. 



SOLAR PARALLAX. 



In an elaborate paper, given in full in the Atnerican 

 Journal of Science, for November, Professor William 

 Harkness draws the following conclusions : — 



For convenience of reference the limiting values of 

 the solar parallax, found by the various methods de- 

 scribed in the foregoing pages, are presented here. It 

 should be remarked, however, that in selecting these 

 values the results of all discussions made prior to 1857 

 have been omitted ; except in the case of the transit of 

 1761, and the smaller of the two values from the transit 

 of 1769. 



I. — Trigonometrical methods. 



Mars, meridian observations 8". 84 — 8". 96 



" diurnal observations 8.60 — 8.79 



Astjeroids 8.76 — 8.88 



Transit of Venus, 1761 8.49 — 10.10 



1769 8.55 — 8.91 



1874 8.76 — 8.85 



II. — Gravitational methods. 



Mass of the earth 8".87 ± o".o7 



Parallactic Inequality 8.78 — 8.91 



Lunar Inequality 8.66 — 9.07 



III. — Photo- tachymetrical methods. 



Velocity and light equation 8". 72 — 8". 89 



Velocity and Aberration 8.73 — 8.90 



To obtain a definite value of the solar parallax, it 

 would now be necessary to form equations of condition 

 embodying the relations between the various elements in- 

 volved ; to weight these equations ; and to solve for it 

 by the method of least squares. But what is the use? 

 It is perfectly evident that by adopting suitable weights, 

 almost any value from 8". 8 to 8". 9 could be obtained, 

 and no matter what the result actually was, it would al- 

 ways be open to a suspicion of having been cooked in 

 the weighting. We only know that the parallax seems 

 to lie between 8". 75 and 8". 90, and is probably about 

 8 ".85. Attack the problem as we will, the results clus- 

 ter around this central value. All the methods give a 

 probable error of about ±o".o6, and no one of them 

 seems to possess decided superiority -over the others. 

 We have nearly exhausted the powers of our instru- 

 ments, and further advance can only be made at the 

 cost of excessive labor. 



In the beginning of the eighteenth century the uncer- 

 tainty of the solar parallax was fully two seconds ; now 

 it is only about o".i5. To narrow it still further, we re- 

 quire a better knowledge of the masses of the earth and 

 moon, of the moon's parallactic inequality, of the lunar 

 equation of the earth, of the constants of nutation and 

 aberration, of the velocity of light, and of the light 

 equation. All these investigations can be carried on at 

 any time, but there are others equally important which 

 can only be prosecuted when the planets come into the 

 requisite positions. Among the latter are observations 

 of Mars when in opposition at its least distance from the 

 earth, and transits of Venus- 



In 1S74 all astronomers hoped and believed that the 

 transit of Venus which occurred in December of that 

 year would give the solar parallax within o".oi. These 

 hopes were doomed to disappointment, and now, when 

 we are approaching the second transit of the pair, there 

 is less enthusiasm than there was eight years ago. Nev- 

 ertheless the astronomers of the twentieth century will 

 not hold us guiltless if we neglect in any respect the 

 transit of 1882. Observations of contacts will doubt- 

 less be made in abundance, but our efforts should not 

 cease with them. We have seen that the probable error 

 of a contact observation is ±0". 15, that there may always 

 be a doubt as to the phase observed, and that a passing 

 cloud may cause the loss of the transit. On the other 

 hand, the photographic method cannot be defeated by 

 passing clouds, is not liable to any uncertainty of inter- 

 pretation, seems to be free from systematic errors, and is 

 so accurate that the result from a single negative has a 

 probable error of only ±o".S5. If the sun is visible for 

 so much as fifteen minutes during the whole transit, 

 thirty-two negatives can be taken, and they will give as 

 accurate a result as the observation of both internal con- 

 tacts. In view of these facts, can it be doubted that the 

 photographic method offers as much accuracy as the 

 contact method, and many more chances of success? 



The transit of 1882 will not settle the value of the solar 

 parallax, but it will contribute to that result, directly as a 

 trigonometrical method, and indirectly through the grav- 

 itational methods with which the final solution of the 

 problem must rest. As our knowledge of the earth's 

 mass may be made to depend upon quantities which con- 

 tinually increase with the time, it will ultimately attain 

 great exactness, and then the solar parallax will be known 

 with the same exactness. Long before that happy day 

 arrives the present generation of astronomers will have 

 passed over to the silent majority, but not without the 

 satisfactien of knowing that their labors will contribute 

 to that fullness of knowledge which shall be the heritage 

 of their successors. 



