Raven was echoing the words Henry once used when he had been called upon to stitch Raven’s cheek. His hand went to the scar as he spoke, by way of reminding him. Henry looked despondent.

‘I jest,’ Raven said. ‘Gabriela, would you fetch my bag from the bedroom?’

‘Thank you,’ said Henry. ‘It’s not so much for the pain, as to spare me the greater agony of witnessing your ham-fisted butchery upon my leg.’

‘Oh, don’t be so precious. You have another.’

Raven pulled the knife from his pocket. Henry’s eyes were immediately drawn to the blade, noticing that it was blood-smeared. Raven hoped that in his delirium he did not think to wonder how.

‘I hope you’re going to wash that thing first. Remember Semmelweis.’

Henry was referring to a doctor he had spoken to in Vienna. Semmelweis had published a paper examining the far higher death rate of maternity patients on a ward staffed by medical students compared to one staffed by midwives. He maintained that this was because the students were coming directly from the dissection room without washing their hands, postulating that morbid material was being transferred from the students to the patients. When he made the students wash their hands in chlorinated water, the death rate went down. Despite this, Semmelweis was having difficulty convincing his colleagues that he was right and was venting his frustrations at anyone who would listen. Henry had proven a sympathetic ear.

Raven did not need to be lectured on this subject. For years Simpson had been teaching his students that puerperal fever was a disease transmitted from one patient to another via the attending doctor or midwife.

He bade Liselotte fill some jugs with water and tear up some sheets to make bandages. While she obliged, Raven prepared the chloroform, asking Gabriela to pay close attention in case he required her to administer more while he worked on Henry’s leg.

Raven shaped a small piece of muslin into a cone and proceeded to carefully angle the bottle so that the liquid fell onto the cloth in small drips. He could not help but think of how Dr Simpson’s discovery had preceded him on all his travels. Chloroform was transforming surgery, its use spreading fast. In London he had heard John Snow lecture on the importance of precision and control in the dosage. Raven had then witnessed him demonstrate his vaporiser device, invented for the purpose of administering a quantifiable amount of chloroform. Tonight in Berlin he would be relying on an untrained assistant dropping the liquid from a bottle in poor light, and all of them half drunk.

‘The drops must be small,’ he stressed to Gabriela. ‘So that he does not inhale too much.’

‘Right now I’m concerned with inhaling too little.’

Raven held the cone above Henry’s face.

‘And take care not to let it touch his skin. It is an irritant and apt to leave a mark.’