But it is indubitable that, in spite of the slowness with which medical science is developing, it will in the future reach a degree which will enable us to cease to tremble any longer before all sorts of incurable diseases. Orthobiosis will then appear, no longer under its present incomplete form, but as the solid and essential basis of life. CHAPTER XXXIV Return to St. Léger-en-Yvelines--Norka--Studies on the death of the silk-worm moth--War declared--Mobilisation. The drawback of the holidays consisted, for Metchnikoff, in coming away from his laboratory and in the impossibility of following his diet in a hotel or a boarding-house. We therefore resolved to hire a cottage in some quiet place, to organise a small laboratory, and to continue our usual mode of life. St. Legér-en-Yvelines, where we had spent part of the preceding summer, answered all our requirements. We took a small villa there and called it "Norka," which means in Russian "little hole," "little refuge," and came there for the holidays in July 1914. Elie seemed pleased to be there; thanks to the laboratory, he could easily vary his occupations, for continuous reading fatigued him. His reflections having led him to the problem of natural death, he had for some time been seeking for a subject on which he could study the mechanism of the phenomenon. He had formerly studied the May-flies (Ephemeridæ), predestined to a natural death by their rudimentary buccal organs, incapable of use in feeding. But the life of those insects, a life of a few hours or a few days at the most, was too short to allow the necessary researches. The males of the Rotifera, which are also deprived of buccal organs and even of digestive organs, were too small in size for physiological experiments. Thus, those two examples of natural death among multicellular beings were unsuitable to the projected study. He found a more favourable subject in the moth of the silk-worm (_Bombyx mori_); the rudimentary buccal organs of that insect make all feeding impossible and predestine it to a natural death. The dimensions of the silk-worm moth are large enough and it has a life duration of twenty-five or thirty days, therefore sufficient to allow the study of the mechanism by which its death is brought about. Metchnikoff procured a quantity of silk-worms, and soon the moths hatched and covered all the mantelpieces and tables in Norka with white flakes. He ascertained that it was not hunger which brought about the death of the moths, for their organism was not in the least exhausted.