What the boy doesn’t know – can’t know – was that the monkey leaves part of itself behind. In the scuffle, it has shed three of its fleas.
One of these fleas falls, unseen, to the ground, where the boy will unwittingly crush it with the sole of his foot. The second stays for a while in the sandy hair of the boy, making its way to the front of his crown. When he is paying for a flagon of the local brew in the tavern, it will make a leap – an agile, arching spring – from his forehead to the shoulder of the innkeeper.
The third of the monkey’s fleas will remain where it fell, in the fold of the red cloth tied around the boy’s neck, given to him by his sweetheart at home.
Later, when the boy has returned to the ship for the night, having eaten a dinner of some of the spiced nuts and a curious patty of bread, shaped like a pancake, he will pick up his favourite of the ship’s cats, an animal mostly white but with a striped tail, and nuzzle it against his neck. The flea, alert to the presence of a new host, will transfer itself from the boy’s neckerchief, to the thick, milk-white fur of the cat’s neck.
This cat, feeling unwell, and with the feline’s unerring eye for those who dislike it, will take up residence, the next day, in the hammock of the midshipman. When he, that night, comes to his hammock, he will curse at the now-dead animal he finds there, turn it unceremoniously out, kicking it across the room.
Four or five fleas, one of which once belonged to the monkey, will remain where the cat lay. The monkey’s flea is a clever one, intent on its survival and success in the world. It makes its way, by springing and leaping, to the fecund and damp armpit of the sleeping, snoring midshipman, there to gorge itself on rich, alcohol-laced sailor blood.
The flea from the monkey is, of course, infected with pestilence, and immediately causes havoc on the ship. A bit further in the text, the following happens:
Unbeknown to them both, the flea that came from the Alexandrian monkey – which has, for the last week or so, been living on a rat, and before that the cook, who died near Aleppo – leaps from the boy to the sleeve of the master glassmaker, whereupon it makes its way up to his left ear, and it bites him there, behind the lobe. He doesn’t feel it as the cool air of the misty canal has rendered his extremities sensationless, and he is intent only on getting these boxes of beads aboard the ship, receiving his payment, then returning to Murano, where he has many orders to fulfil and the fire stokers are sure to be fighting again, during his brief absence.
And so on. It is all very cinematographic, and would have made a gripping disaster movie. But listening to this, I kept thinking about the chapter on microbiology I had read way back when, and how it described how Yersinia pestis, the plague bacillus, obstructs the digestive tract of the flea causing it to regurgitate the swallowed blood — now infected with the bacterium — back into the wound; and couldn't help wondering, how long such a flea with a blockage in its gut would survive. Would it stay alive for over a week as the author makes it do?