48o 



second investigation entirely confirms the accuracy of the 

 first as regards the periodic inequalities, but that the 

 secular variations of the excentricity and longitude of the 

 perihelion are slightly changed. The effect of these 

 changes is to bring the theory into very satisfactory 

 accordance widi the observations of Bradley, but the dis- 

 crepancies above mentioned in the time of Maskelyne 

 and in the modern observations still remain unaffected. 

 7 he character of the discrepancies shown by the modern 

 observations makes it very improbable that they can be 

 due to any errors in the theory. 



In fact, the error appears lo change almost suddenly 

 from a positive one of 4" 4 in 1S39 to a negative one of 

 5"'o in 1844, a variation of nearly 9"'5 in five years. Now 

 no terms or group of terms due to tlic action of the 

 planets could thus suddenly disturb the motion in five 

 years, at a given epoch, and then leave the motion 

 unaffected during the following twenty-five years. M. 

 Leverrier is therefore inclined to think that the discre- 

 pancies arise from errors in the observations, notwith- 

 standing that the Greenwich and Paris observations are 

 mutually confirmatory of each other. 



He suggests that it is possible that the varying aspects 

 presented at different times by the ring may affect the 

 accuracy of the observations of the planet, and may cause 

 changes in the personal equations of the observers, which, 

 from being rather large in the case of the ancient observa- 

 tions, have gone on diminishing as the system of 

 observation has become more perfect. 



One unlooked-for result follows from M. Leverrier's 

 comparison of his theory of Saturn with the observations. 

 Considering that the iniluence of Jupiter on the longitude 

 of Saturn may amount to 3800", it might have been 

 expected that from observations of the planet extending 

 over 120 years the mass of Jupiter could have been deter- 

 mined with great precision. INI. Leverrier has found, how- 

 ever, that this is not the case. 



The equations cf condition furnished by the comparison 

 of the heliocentric longitudes of Saturn as deduced from 

 theory and observation contain five unknown quantities, 

 viz., the corrections of the assumed values of four 

 elements and the correction of the assumed mass of 

 Jupiter. On solving the equations with respect to the 

 first four unknown quantities, the corrections to be 

 applied to the elements are found to be greatly influ- 

 enced by the intermediate correction of the mass of 

 Jupiter, and after they have been substituted in the 

 equations of condition, the coefficients of the correc- 

 tion of the mass of Jupiter in great part destroy each 

 other, nowhere amounting in the resulting equations to 

 one-tenth part of their values in the primitive equations. 

 Hence these equations are insufficient to determine the 

 mass of Jupiter with any precision. Consequently, in the 

 formation of the Tables of Saturn, M. Leverrier has 

 employed the value of the mass of Jupiter determined by 

 the Astronomer-Royal from his observations of the 4th 

 satellite. 



The result which has just been noticed will appear to 

 be less paradoxical if we consider that by far the larger 

 part of the disturbances which Jupiter produces in the 

 motion of Saturn is represented by the inequalities of 

 long period which affect the mean longitude and the 

 elements of the orbit. Now in the course of 120 years 

 these inequalities have run through only a small part of 

 their whole period, and therefore, during this interval, the 

 greater part of their effects may be represented by 

 applying changes to the several mean elements equal to 

 the mean value of the corresponding long inequalities 

 during the interval. It is only from the residual disturb- 

 ances, which arc comparatively small in amount, that 

 any data can be obtained for the correction of the mass 

 of Jupiter. 



In the course of a few centuries, when these long 

 inequaUties, as well as the secular variations of the 



NATURE [Oct. 4, 1877 



elements of Saturn, shall have had time to develop them- 

 selves, it will be possible to determine the mass of Jupiter 

 from them with all desirable precision. 



TBE GLANDULAR ORIGIN OF CONTAGIOUS 



DISEASES -> 

 'X'EN years ago, on the occasion of a Congress held in 

 -*- this town to discuss the question of the disposal of 

 sewage, I had the honour, at the request of the committee 

 of management, to deliver a lecture on the subject of the 

 poisons of the spreading or communicable diseases. An 

 abstract of the lecture was afterwards printed by the 

 Congress, and for a time it gained a wide circulation. 



The lecture of which I speak was based on a series of 

 experimental reiearches which for some years previously 

 I had been carrying out on the question of the mode of 

 production and communication of those diseases which 

 were anciently called plagues or pestilences, but which 

 are now called communicable or spreading diseases. 



I do not think that at a health congress like the present 

 I can do better than recall attention to this same subject. 

 The suppression of plagues is one of the grandest and 

 supremest efforts of the sanitary reformer. The sup- 

 pression can never be accomplished until all educated 

 people understand the advances of modern science as to 

 the cause and mode of origin and mode of propagation 

 of these diseases. Whatever, therefore, tends to strike 

 out light of knowledge on these subjects tends to eluci- 

 date, and though the spark lighted may go out again it 

 may help to show the way. 



I shall in this present effort first go back to the point 

 where I stood when here ten years ago. I shall then 

 briefly survey the course of thought that has sprung up 

 between that time and the present. Next I shall state 

 the position of my own views as influenced by the work 

 of the past ten years. Lastly, I shall tojch for a moment 

 or two on the practical applications of theory to the deve- 

 lopment of practice. 



Oil/ line of the Glaiidular Theory. 



From my researches previous to the year 1S67, and 

 which formed the subject-matter of my previous lecture 

 here, I had discovered that the fluids secreted during 

 various stages of disease in some forms of communicable 

 disease could be made to propagate diseiss. A portion 

 of secreted fluid taken from a patient of Mr. Spencer 

 Wells, a patient who was suffering from surgical fever 

 following upon the operation of ovariotomy, had been 

 made to produce a definite form of fever in an inferior 

 animal by being simply brought into contact with the 

 peritoneal surface of the animal. The secretion from the 

 peritoneum of the affected anim\! was shown by further 

 experiments to have the power of inducing the same order 

 of phenomena of disease in other similar animals, and 

 through four generations of animals the phenomena were 

 repeated. These were the first experiments in which this 

 class of phenoaiena of disease by direct propagation and 

 repropagation were produced synthetically. They have 

 since been performed and modified in many ways, and 

 the origination of them has been assigned to different 

 experimentalists, but I am entitled to say they were the 

 first of the kind ; they were carried out in the years 

 1864-65, and they were communicated to the Association 

 of Medic-il Officers of Health in the year 1S65. 



Duiing the same course of research I made an attempt 

 to separate the poisonous matter from the poisonous 

 secretion, and in one attempt of the sort I believed myself 

 to have Ijeen successful. Certainly I separated a sub- 

 stance which was exceedingly poisonous in its action, and 

 which, after the manner of an alkaloid, combined with 



' A Theory as tu the Natural or Glandular Origin of tli3 Contagious 

 Diseases. Address by the president. Benjamin W. Richardsjn, M.D., 

 F, R.S. , at the Sanitary Congress, Leamington, October 3. 



