66 



Mr. G. F. DowdeswelL 



VI. Duration of the Incubation Period. 



The great variability of the incubation period and the extreme 

 length to which it may extend after the bite of a rabid animal, is 

 well known, and constitutes the most unaccountable feature of this 

 disease. It is well established that both in man and the lower 

 animals it may extend to at least several months, and even periods of 

 some years have been recorded upon apparently good evidence. Sub- 

 cutaneous inoculation with saliva taken from the mouth in all the 

 experiments which I made failed. In intracranial inoculations with 

 the secretion expressed from the parotid gland, as previously described, 

 the incubation period was seventeen days. 



By subcutaneous inoculation with the medulla of street rabies, it is 

 uncertain and generally prolonged, both in dogs and rabbits, but by 

 intracranial inoculation it is much shortened and more regular. I 

 have had two cases above recorded in rabbits, where the first symptoms 

 appeared on the fourth and seventh days respectively, after intracranial 

 inoculation, but this is most unusual with virus from this source, i.e., 



The most important recent work upon the subject in English is the article by 

 Bollinger, in the Ameiican translation of Ziemssen's ' Cyclopaedia of the Medical 

 Sciences,' which gives a good account of the aetiology of the disease, its symptoms, 

 and other features, both in man and the lower animals, with a notice of the previous 

 literature. 



A copious bibliography is contained in the ' Dictionnaire Encyclopedique des 

 Sciences Medicales,' ed. by A. Dechambre, Paris, 1874, article " Rage." The list 

 is brought up to the date of the commencement of Pasteur's investigation and 

 the inauguration of the present views upon the subject in the ' Nouveau Diction- 

 naire de Medecine et de Chirurgie Pratique,' by Dr. Jaccoud, vol. 30, Paris, 1881. 



The most complete account of the literature of the subject, however, is that given 

 in the invaluable ' Index Catalogue of the Surgeon-G-eneral's Office U.S. Army.' 

 Washington, 1885, vol. 6. Art. " Hydrophobia." 



The communications to the Royal Society upon rabies or hydrophobia have not 

 been numerous or important ; they are mainly records of cases in man and reports 

 of asserted cures. One of these by Dr. James has been above referred to. 



Amongst the more recent publications upon this subject may be mentioned that 

 of M. Bourrel, a veterinary surgeon, formerly in the French Army, and director of 

 the Institution for the Study of Canine Pathology in Paris. His observations 

 (' Traite complet de la Rage, chez le Chien et chez le Chat, Moyen de s'en preserver, 

 &c.,' Paris, 1874) are important on account of the very large number of cases in the 

 dog which he had the opportunity of observing. 



Between the years 1859 and 1872, as he states, out of 18,531 dogs admitted to the 

 establishment 1219 were rabid. He advocates the prompt application of caustic 

 to the bite of a rabid animal, and admits that the enforced muzzling of dogs had 

 been beneficial ; but his specific to abolish all risk to man from this disease is by 

 filing down the points and sharp edges of the canine teeth and incisors of all dogs. 



Since the publication of M. Pasteur's results the only independent investigations 

 as yet recorded are those, before referred to, of Professor Frisch, in Vienna ; and, 

 more recently, in the ' Annales de l'lnstitut Pasteur,' Paris, March, 1887, those of 

 Dr. Bardach, of Odessa, noticed below. 



