The glands are less significant than the heart in the overall function of the body, so he implies that writers have lost the soul in their writing. Writing from the heart consists of very heart-felt and strong emotion, while writing from the glands is superficial and trivial. Writing used to be the product of years of agony and sweat, but now writing is just the product of fear. The sweat represents the way writers used to toil in their work. He repeats agony and sweat both in the first and the second paragraph.
Faulkner states that new writers stories are much less powerful, and they are written without pity or compassion. These more modern writers do not appeal to pathos as much as they used to; but rather, logos. Writing that appeals to logos is not as exciting as writing that appeals to pathos.
This writing without pity or compassion is also tied into how writers do not write of the heart anymore. Writing that appeals to pathos is deeper in meaning and is more directly from the heart, while writing that appeals to logos is more from the logical part of a writer, or his mind. Writers use their minds too much, rather than their heart and soul.