I placed very active curare on the crural nerves of a frog without noticing any change, measuring the degree of its organs' irritability with an arc formed of heterogeneous metals. But these Galvanic experiments hardly worked on birds a few minutes after they had been shot with poison arrows. Curare works only when the poison acts on the vascular system. At Maypures, a colored man (a zambo, a cross between Indian and negro) was preparing one of those poison arrows that are shot in blowpipes, to kill small monkeys or birds for M. Bonpland. He was a carpenter of extraordinary strength. He stupidly rubbed the curare between slightly bleeding fingers and fell to the ground, dizzy for half an hour. Luckily it was a weak curare (destemplado), used for small animals, which may be revived later by placing muriate of soda in the wound. During our journey back from Esmeralda to Atures. I escaped from danger myself. The curare had attracted humidity and become liquid and spilled from a poorly closed jar on to our clothes. We forgot to check the inside of a sock filled with curare when washing our clothes. Just touching this sticky stuff with my hand I realized I should not pull on the poison sock. The danger was all the greater as my toes were bleeding from chigoe wounds.

We passed the night of the 20th of May, the last on the Casiquiare, near the bifurcation with the Orinoco. We hoped to make some astronomical observations as we saw extraordinary shooting stars visible through the mist. Indians, who do not embellish their imagination through words, call shooting stars the 'piss of the stars', and dew the 'spit of the stars'. But the clouds thickened and prevented us from seeing both meteors and stars.

The Chaimas have attractive white teeth like all who lead a very simple life, but not as strong as negro teeth. The early explorers noted their custom of blacking their teeth with plant juices and quicklime; today this custom has disappeared. I doubt whether the custom of blacking their teeth had anything to do with odd ideas about beauty or a remedy against toothache. It could be said that Indians do not know toothache, and Spaniards who live in the Tropics do not suffer from this pain either.

The passage from the mouth of the Río Negro to Grand Para took only twenty to twenty-five days, so we could have gone down the Amazon as far as the Brazilian coast just as easily as returning by the Casiquiare to Caracas. We were told at San Carlos that political circumstances made it difficult to cross from Spanish to Portuguese colonies, but we did not know until our return to Europe what danger we would have been exposed to had we gone as far as Barcellos. It was known in Brazil, probably through newspapers, whose indiscretion is not helpful for travelers, that I was going to visit the Río Negro missions and examine the natural canal uniting the two river systems. In these deserted jungles the only instruments ever seen had been carried by the boundary commissioners. The Portuguese Government agents could not conceive how a sensible man could exhaust himself 'measuring lands that did not belong to him'. Orders had been issued to arrest me, seize my instruments, and especially my astronomical observations, so dangerous to the safety of the State. We were to be led along the Amazon to Grand Para, and then back to Lisbon. Fortunately, the Lisbon Government instantly ordered that I should not be disturbed but rather encouraged.

As rain was pouring down we had to sleep in the overcrowded hut. The Indians slept only from eight at night to two in the morning; the rest of the time they chatted and prepared their bitter cupana drink, poking the fire and complaining of the cold, even though the temperature was 21°C. This custom of staying awake, even of getting up four or five hours before dawn, is common to the Guiana Indians.

We had as travelling companions a Frenchman, Dr Rieux from Carcassonne, and the young son of the ill-fated Nariìo. The bad luck of these two moved us, reminding us of the state of oppression in this unhappy country. Dr Rieux, a charming, educated man, had come from Europe as doctor to Viceroy Ezpeleta. He was accused of interfering in politics, dragged out of his house in Honda in 1794, clapped in irons and taken to the inquisition prison in Cartagena. This damp place caused him a chronic blindness. For more than a year his wife had no news of his whereabouts. His belongings were dispersed and, as nothing could be proved, he was sent (bajo partido de registro) to Càdiz prison where his case would be forgotten. He managed to escape off the African coast.

The Casiquiare Indians, though easily reverting to barbaric customs, show some intelligence in the missions, work well and learn Spanish. As most missions have two or three tribes speaking different languages the language of the missionaries lets them communicate with each other. I saw a Poignave Indian talk in Castilian with a Guahibo, though both had left the jungle only three months before. Every quarter of an hour one spoke a carefully prepared phrase in which the verb, following the grammar of their own languages, was always a gerund ('When me seeing the father, the father me saying...').