Early in 1870, Bernard performed more research on carbon monoxide poisoning: with Paul Bert now at the Sorbonne, his new préparateur Louis Ranvier (whose interest in neuroanatomy and neurophysiology would later win him acclaim) assisted him in his studies on the interactions of blood gases.188,189,193  Bernard was also now planning his lecture and research program for the Natural History Museum; on the comparative physiology of plants and animals.207 

In July 1870, and shortly after Bernard's inaugural lecture at the Museum192, Louis Napoleon declared war on Germany. This was prompted by Germany's escalating military power, and its equally worrying 'gift' to the Spanish throne of a Prussian royal.  Kaiser Wilhelm refused to address Louis-Napoleon's concern about what he saw as a threat to France on two flanks. Germany accepted the challenge to battle. Together with so many others, Bernard escaped from Paris just as the Kaiser's troops got the upper hand, invading southwards from Alsace and Lorraine. At his country refuge even further south in St Julien, Bernard continued to prepare his lectures for the Museum and the Collège, and crystallized his ideas on body heat: not only its generation, but the effect that the temperature of the blood might have on various biological processes191.

However with the tumult of war, he found it difficult to concentrate. In a singularly cold winter with almost two metres of snow on the ground, he spent his time dealing with the wine-making accounts; and was driven to read novels with which he had little patience, since "...they all ended the same way" (Bernard's library consisted of over one thousand books, of which only two were non-scientific). A high point was a visit from Louis Pasteur who had battled his way through the snow to visit him on his way back from Lorraine. He had been searching for, and eventually found his ill and injured son who had been called up to fight for his country. Together Bernard and Pasteur talked of life and death - and no doubt their conflicting ideas on wine fermentation. 

In mid-1871, Bernard returned to a capital which had been beaten and bruised by a lost war and divisive politics. Fortunately his laboratories were intact, but Lemaistre, his préparateur at the Museum had been killed on the war front, and it took time to rebuild his research program. Over the next months he restricted himself to studies of glycogen and glucose in birds200, slugs, oysters, crayfish and alpine marmots, and comparing the process of glycogen breakdown in animal tissues to that of starch breakdown in plants. He was proud when in 1872, Baillière  published his Leçons in Experimental PathologyTMB39, and soon after Hachette published his Leçons in General PhysiologyTMB40.

An unpleasant episode occurred when he was attacked by the eminent Bouillaud, Dean of the medical faculty: he insisted on publicly supporting Lavoisier's theory (without proof) that the lungs were the sole seat of body heat production.203,204 
As if in compensation, Bernard was chosen to be the first president of the French Association for the Advancement of Science: an acknowledgement - said the press - of his status as the foremost scientist of France. From 1873 onwards, he devoted himself to this responsibility, and to extensive lecturing at the Museum and Collège. With his remaining (and last) préparateur, Arsène d'Arsonval, he continued to experiment on poisons like strychnine and arsenic228: more studies too on the effect of anesthetic agents on plants236,240. The extensive notes of his research, so carefully compiled by Mirko Grmek show that during his last years he was also busy studying alcoholic fermentation, although he never published on that subject.

It  was  above all the period of his writing; of drawing his ideas together: on asphyxia189,198 and anesthesia236,240, on animal heat225,241, on experimental science233,243, on diabetes218,234,235 and the role of glycogen231,244,247; and again on the phenomena common to animals and plants236,239,240.

Bernard always denied that he was a philosopher, although his Introduction still figures on the reading list for philosophy students more than a century and a half later. There has been much argument about whether positivisme remained an important element of his scientific approach. Although Bernard denied that it did, the direction of his experiments does not support his words. Certainly, he became better known for scientific (or experimental) determinism. He never changed the views expressed in his 'Introduction': and he repeatedly stressed the importance of the concept in reporting his research findings in lectures and writings. Numerous eminent philosophers dwell upon his 'philosophy', but it is only in his Introduction and in his Definition de la Vie 226 that one gets any impression of his philosophical principles.

During the latter half of 1877, it was clear that his energy was failing him. He had often to be helped by his maid across the rue des Écoles to the Collège, and he spent longer periods in his apartment, cossetted by Madame Raffalovich and increasingly visited by his colleagues with reading matter and academic gossip. Finally he was bed-bound. One evening, as his legs were being covered with a travelling rug, he commented: "This time it will serve me for the voyage from which there is no return; the voyage of eternity."

Claude Bernard died in his apartment on February 10th, 1878. Present at the time were his maid Mariette Rey, d'Arsonval, Madame Raffalovich and her daughter Sophie, but neither of his daughters. 

                                     An Important Epilogue......